US20040131888A1 - Magnetic sensor - Google Patents
Magnetic sensor Download PDFInfo
- Publication number
- US20040131888A1 US20040131888A1 US10/736,015 US73601503A US2004131888A1 US 20040131888 A1 US20040131888 A1 US 20040131888A1 US 73601503 A US73601503 A US 73601503A US 2004131888 A1 US2004131888 A1 US 2004131888A1
- Authority
- US
- United States
- Prior art keywords
- magnetic
- sensor
- layer
- ferromagnetic
- spin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 230000005291 magnetic effect Effects 0.000 title claims abstract description 218
- 230000005294 ferromagnetic effect Effects 0.000 claims description 55
- 230000005415 magnetization Effects 0.000 claims description 45
- 239000000463 material Substances 0.000 claims description 11
- 239000004065 semiconductor Substances 0.000 claims description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 6
- 229910045601 alloy Inorganic materials 0.000 claims description 5
- 239000000956 alloy Substances 0.000 claims description 5
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- 239000010941 cobalt Substances 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 150000002739 metals Chemical class 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 2
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 claims description 2
- KXNLCSXBJCPWGL-UHFFFAOYSA-N [Ga].[As].[In] Chemical compound [Ga].[As].[In] KXNLCSXBJCPWGL-UHFFFAOYSA-N 0.000 claims description 2
- AUCDRFABNLOFRE-UHFFFAOYSA-N alumane;indium Chemical compound [AlH3].[In] AUCDRFABNLOFRE-UHFFFAOYSA-N 0.000 claims description 2
- 229910052782 aluminium Inorganic materials 0.000 claims description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 2
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 239000011651 chromium Substances 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 239000010949 copper Substances 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 20
- 230000035945 sensitivity Effects 0.000 description 8
- 239000010408 film Substances 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 4
- 230000004044 response Effects 0.000 description 4
- 230000005290 antiferromagnetic effect Effects 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000010409 thin film Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000003302 ferromagnetic material Substances 0.000 description 2
- 239000000696 magnetic material Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- -1 for example Substances 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910000889 permalloy Inorganic materials 0.000 description 1
- 229910000702 sendust Inorganic materials 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66984—Devices using spin polarized carriers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
- G01R33/09—Magnetoresistive devices
- G01R33/093—Magnetoresistive devices using multilayer structures, e.g. giant magnetoresistance sensors
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/33—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only
- G11B5/39—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects
- G11B5/3903—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects using magnetic thin film layers or their effects, the films being part of integrated structures
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/33—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only
- G11B5/39—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects
- G11B2005/3996—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/11—Magnetic recording head
- Y10T428/1107—Magnetoresistive
Definitions
- the present invention relates to a magnetic sensor, and more particularly, to a magnetic sensor that uses a spin-filtered sensor current to provide high-density recording and reproduction of information to and from a hard disk or other such magnetic recording medium.
- MR magneto-resistive
- AMR anisotropic magneto-resistive
- GMR giant magneto-resistive
- a so-called spin-valve structure employing four basic layers is commonly used for the GMR film.
- the four layers of the spin-valve structure are an anti-ferromagnetic layer, a fixed magnetic layer, a non-magnetic metallic layer and a free magnetic layer.
- the above-described object of the present invention is achieved by a magnetic sensor that senses an external magnetic field using a spin-filtered sensor current flowing through a non-magnetic layer.
- the use of a spin-filtered sensor current flowing through a non-magnetic layer provides a magnetic sensor with improved sensitivity.
- the above-described object of the present invention is also achieved by the magnetic sensor as described above, further having:
- a power source that uses the ferromagnetic bodies as electrodes to supply the sensor current.
- a ferromagnetic film is provided on the non-magnetic layer.
- an axis of magnetization of the ferromagnetic layer is formed either parallel to or opposite to a direction of electron spin of the sensor current.
- the above-described object of the present invention is also achieved by the magnetic sensor as described above, wherein the ferromagnetic layer is formed as a free layer constituting either an anisotropic magneto-resistive film or a giant magneto-resistive film.
- the non-magnetic layer is formed of a semiconductor material
- the axis of magnetization of one of the pair of ferromagnetic bodies changes so as to detect an external magnetic field.
- FIGS. 1A and 1B are schematic diagrams illustrating a basic structure of an MR sensor adapting the present invention
- FIG. 2 is a diagram illustrating the operating principles of a conventional sensor employing a GMR structure, and specifically, changes in a resistance of a magnetic layer in response to changes in direction of an external magnetic field;
- FIG. 3 is a diagram illustrating an operation of an MR sensor employing the magnetic sensor according to the present invention, and specifically, changes in a resistance of a magnetic layer in response to changes in direction of an external magnetic field;
- FIG. 4 is a schematic diagram showing a basic structure of a spin filter
- FIG. 5 is a diagram showing a magnetic sensor according to a first embodiment of the present invention.
- FIG. 6 is a diagram showing a magnetic sensor according to a second embodiment of the present invention.
- FIG. 7 is a diagram showing a magnetic sensor according to a third embodiment of the present invention.
- FIGS. 8A and 8B are diagrams illustrating an operation by which the magnetic sensor shown in FIG. 7 detects a magnetic field
- FIG. 9 is a lateral cross-sectional view of a magnetic recording and/or reproduction device employing the magnetic sensor according to the present invention.
- FIG. 10 is a diagram showing a plan view of the magnetic recording and/or reproduction device shown in FIG. 9.
- the magnetic sensor according to the present invention represents a new structure as compared to the conventional magnetic sensors using AMR or GMR structures. That is, the direction of magnetization of the ferromagnetic layers is set to be either parallel to or opposite to the spin of the electrons that make up the sensor current that flows through a non-magnetic layer. The direction of magnetization of one of the ferromagnetic layers then rotates when exposed to a signal magnetic field (external magnetic field) from the magnetic recording medium being read. When the direction of magnetization of the ferromagnetic layer is opposite to the spin orientation of the electrons, the magnetic resistance is at its strongest.
- MRR Magnetic Resistance Ratio
- the magnetic sensor according to the present invention uses either changes in magnetic resistance or else switches a semiconductor material on and off to sense signal magnetic fields (external magnetic fields) from a recording medium.
- the basic structure of the magnetic sensor used in order to detect the signal magnetic fields from the magnetic recording medium involves a ferromagnetic layer and a non-magnetic layer.
- the signal magnetic field emanating from the recording medium can be detected with a high degree of sensitivity.
- FIGS. 1A and 1B are schematic diagrams illustrating a basic structure of an MR sensor according to the present invention.
- FIG. 1A the direction of magnetization of the ferromagnetic layer and the direction of spin of the electrons of the sensor current flowing through the non-magnetic layer are parallel, whereas in FIG. 1B the two directions are opposed.
- a magnetic resistance R in the state depicted in FIG. 1A is a minimum value RS.
- FIG. 1B is the opposite of the state shown in FIG. 1A.
- the direction of magnetization of the ferromagnetic layer 1 is upward, and the electrons 5 that form the sense current flow from bottom to top as is the case in FIG. 1A, but the direction of spin of the electrons 5 within the non-magnetic layer 3 is downward.
- the magnetic resistance R of the state shown in FIG. 1B is a maximum value RL.
- the MR sensor of the present invention uses the states shown in 1 A and 1 B above to sense a signal magnetic field from the magnetic recording medium.
- the MRR can be increased and thus detection sensitivity improved.
- the above-described MRR can be defined using the following formula, by which the MRR is calculated using both the maximum magnetic resistance value RL obtained when the magnetization direction 2 of the ferromagnetic layer 1 and the direction of the spin electron 4 B are opposed as well as the minimum magnetic resistance value RS obtained when the magnetization direction 2 of the ferromagnetic layer 1 and the direction of the spin electron 4 B are parallel:
- FIG. 2 is a diagram illustrating the operating principles of a conventional MR sensor employing a GMR structure, and specifically, changes in a resistance of a magnetic layer in response to changes in direction of an external magnetic field.
- the conventional GMR structure 10 includes, from bottom up, a free magnetic layer 11 , a non-magnetic layer 12 and a fixed magnetic layer 13 . It should be noted that the actual GMR structure 10 also has an anti-ferromagnetic layer, a bias layer, and so forth, although in this diagram only those layers that affect changes in the magnetic resistance are included.
- the sensor current that flows through the non-magnetic layer 12 is not subjected to forces that would control the spin of the electrons and hence is not in a spin-filtered state. Accordingly, electrons with an upward spin orientation and a downward spin orientation are mixed together and each behaves independently.
- FIG. 3 is a diagram illustrating an operation of an MR sensor employing a GMR structure according to the present invention, and specifically, changes in resistance of a magnetic layer in response to changes in direction of an external magnetic field.
- a GMR 20 also includes, from bottom up, a free magnetic layer 21 , a nonmagnetic layer 22 and a fixed magnetic layer 23 .
- the GMR 20 shown in FIG. 3 gives the electrons of the sensor current flowing inside the non-magnetic layer 22 a right-hand spin.
- the electron spin is controlled so as to be of one direction only, so that the two types of magnetic resistance states for each of the conditions shown as (a) and (b) in FIG. 2 in the conventional arrangement do not arise but, instead, only one such resistance state exists for each of the two conditions shown. In other words, in the state shown as (a) in the middle of FIG.
- the boundary of the free magnetic layer 21 with the non-magnetic layer 22 acquires a small resistance RS and only a small resistance RS
- the boundary of the fixed magnetic layer 23 acquires a large resistance RL and only a large resistance RL.
- the MR sensor shown in FIG. 3 forms only a single resistance state for each of the conditions shown in (a) and (b) of FIG. 3.
- the present invention approximately triples the MRR of an MR sensor using a GMR structure as described above, and is thus capable of being employed as the magnetic sensor in a reproduction head.
- the GMR 20 depicted in FIG. 3 can be constructed by converting the two ferromagnetic layers 1 shown in FIG. 1 into the free magnetic layer 21 of FIG. 3 and by converting the non-magnetic layer 3 into the non-magnetic layer 22 .
- FIG. 4 is a schematic diagram showing a basic structure of a spin filter, employed for the purpose of filtering the spin of the electrons that form the sensor current that flows through the non-magnetic layer.
- a pair of ferromagnetic bodies are disposed one at each end of a non-magnetic layer 31 .
- the ferromagnetic bodies 32 , 33 are electrically conductive and function as terminal electrodes.
- the non-magnetic layer 31 can be made of some electrically conductive non-magnetic material such as aluminum, copper, chromium or some alloy of these. Additionally, the ferromagnetic bodies can be formed of a conductive ferromagnetic material selected from among iron, cobalt, nickel or an alloy of these. Attaching a power source 35 to the ferromagnetic bodies 32 , 33 in order to supply the sense current forms the basic structure of the spin filter.
- FIG. 5 is a diagram showing a magnetic sensor according to a first embodiment of the present invention.
- the MR sensor 40 is a simple structure, in which an AMR structure 41 adjoins a bottom surface of the spin filter 30 .
- the AMR structure 41 may be made of the conventional permalloy or Sendust.
- the axis of magnetization 42 of the AMR structure 41 is set so as to be either parallel to or opposed to the direction of spin of the electrons of the non-magnetic layer 31 .
- an external signal magnetic field Hsig When exposed to an external signal magnetic field Hsig the direction of magnetization 42 of the AMR structure 41 rotates, detecting magnetically recorded information as changes in magnetic resistance.
- the two-layer MR sensor of the present embodiment owes its improved sensitivity to a fivefold increase in MRR as compared to the conventional MR sensor described above.
- the above-described MR sensor 40 can be manufactured by commonly known thin film technologies, such as, for example, spattering, development using resist masks, and etching methods.
- FIG. 6 is a diagram showing a magnetic sensor according to a second embodiment of the present invention.
- an MR sensor 50 employs a spin-valve structure on a GMR structure.
- the spin valve structure is a multilayer structure employing a free magnetic layer, a non-magnetic layer, a fixed magnetic layer and an antimagnetic layer.
- the free magnetic layer and the non-magnetic layer, as described above, are designed to control the electron spin by means of the spin filter 30 described above.
- the spin valve type MR sensor 50 of the second embodiment has a free magnetic layer 51 on top of the non-magnetic layer 31 A, and, below the non-magnetic layer 31 , a fixed magnetic layer 52 and an anti-ferromagnetic layer 53 for pinning the fixed magnetic layer 52 .
- the above-described spin-valve structure can be formed using conventional thin film technology.
- the direction of magnetization 54 of the free magnetic layer 51 is set to be either parallel to or opposed to the direction of spin of the electrons of the non-magnetic layer 31 A.
- Hsig an external signal magnetic field
- the direction of magnetization 54 of the free magnetic layer 51 rotates, detecting magnetically recorded information as changes in magnetic resistance.
- the MR sensor using the spin-valve structure shown in the second embodiment described above owes its improved sensitivity to the threefold increase in MRR as compared to the conventional MR sensor described above with reference to FIG. 3.
- FIG. 7 is a diagram showing a magnetic sensor according to a third embodiment of the present invention.
- the first and second embodiments used changes in magnetic resistance arising from the relation between the direction of magnetization of the ferromagnetic layers and the direction of spin of the electrons that form the sensor current that flows through the non-magnetic layer in order to detect an external magnetic field.
- the third embodiment is an FET-type magnetic sensor, in which the non-magnetic layer is formed of a semiconductor material and which detects the presence of an external magnetic field by switching ON and OFF.
- the magnetic sensor 60 has a structure like that of the spin filter 30 shown in FIG. 4. Ferromagnetic bodies 62 , 63 are disposed one at each end atop the non-magnetic layer 61 and function as electrodes. The axes of magnetization of the ferromagnetic bodies 62 , 63 are set parallel (in the case of FIG. 7, both move to the right).
- the non-magnetic layer is made of a semiconductor material, for example indium aluminum arsenide or indium gallium arsenide, so that when an electric current is supplied to the ferromagnetic bodies 62 , 63 from the power source 35 , as shown in FIG. 7 a spin-filtered sensor current flows through the non-magnetic layer.
- a spin-filtered FET is disclosed for example in S. Datra and B. Das, Appl. Phys. Lett. 56 665 (1990), though no mention is made of the applications of such a structure.
- the spin-filtered FET is used to detect the signal magnetic field emanating from the magnetic recording medium, the operation of which is described with reference to FIGS. 8A and 8B.
- FIGS. 8A and 8B are diagrams illustrating an operation by which the magnetic sensor shown in FIG. 7 detects a magnetic field.
- FIGS. 8A and 8B the above-described magnetic sensor 60 is disposed perpendicular to a magnetic recording medium which, in this case, is a hard disk 70 .
- FIG. 8A shows detection at a position at which adjacent magnetizations recorded on the surface of the disk come together
- FIG. 8B shows detection at a position at which adjacent magnetizations recorded on the surface of the disk face away from each other.
- FIG. 8A the direction of the signal magnetic field emanating from the hard disk 70 and the direction of magnetization of the ferromagnetic body 62 are parallel, the spin-filtered sensor current shown in FIG. 7 flows from the ferromagnetic body 62 to the ferromagnetic body 63 , and the semiconductor turns ON.
- FIG. 8B the direction of the signal magnetic field emanating from the hard disk 70 and the initial direction of magnetization of the ferromagnetic body 62 are opposed, thus causing the magnetization direction of the ferromagnetic body 62 to invert so as to become parallel with the direction of the signal magnetic field.
- the magnetic sensor uses the switching effect of a semiconductor to detect the external magnetic field.
- the magnetic sensor 60 can be manufactured using conventional semiconductor production technology or thin film technology.
- the ferromagnetic bodies 62 and 63 can be formed from an electrically conductive ferromagnetic material such as, for example, iron, cobalt, nickel, or an alloy of these metals. Additionally, both the ferromagnetic bodies 62 and 63 need not be made of the same material. However, the direction of magnetization of the ferromagnetic body 62 must be capable of rotating upon contact with a signal magnetic field while the direction of magnetization of the ferromagnetic body 63 must remain fixed in a single direction.
- FIG. 9 is a lateral cross-sectional view of a magnetic recording and/or reproduction apparatus (hereinafter magnetic recording/reproduction apparatus) employing the magnetic sensor according to the present invention.
- FIG. 10 is a diagram showing a plan view of the magnetic recording/reproduction apparatus shown in FIG. 9.
- the reproduction head used in the magnetic recording/reproduction apparatus employs a spin-filtered sensor current to detect information recorded on a magnetic recording medium.
- the magnetic recording/reproduction apparatus comprises a housing 113 and, inside the housing 113 , a motor 114 , a hub 115 , a plurality of magnetic recording media 116 , a plurality of recording/reproduction heads 117 , a plurality of suspensions 118 , and a plurality of arms 119 and actuator units 120 .
- the recording media 116 are mounted on the hub 115 , which is in turn rotated by the motor 114 .
- Each of the recording/reproduction heads 117 is a compound head consisting of a reproduction head shown in any one of FIGS. 5, 6 and 7 as well as an inductive type recording head.
- Each recording/reproduction head 117 is mounted at a tip of a corresponding arm 119 via the suspension 118 .
- Each arm 119 is driven by an actuator unit 120 .
- the basic structure of the magnetic recording/reproduction apparatus as such is well known and so a detailed description thereof will be omitted.
- the number of magnetic recording media 116 is not limited to three but may be 1, 2, or 4 or more such media.
- the types of magnetic recording media need not be limited to the magnetic disks used here.
Abstract
A magnetic sensor senses an external magnetic field using a spin-filtered sensor current flowing through a non-magnetic layer.
Description
- 1. Field of the Invention
- The present invention relates to a magnetic sensor, and more particularly, to a magnetic sensor that uses a spin-filtered sensor current to provide high-density recording and reproduction of information to and from a hard disk or other such magnetic recording medium.
- 2. Description of Related Art
- Computers employing hard disk drives and other magnetic recording and reproduction units continue to require ever greater abilities to record information densely and to reproduce such densely recorded information accurately, which in turn means creating ever more sensitive magnetic sensors.
- Specifically, as the recording density of the recording medium increases, the size of the leakage magnetic field (the signal magnetic field) from each bit decreases, which in turn has lead to proposals for magnetic reproduction heads mounting more sensitive sensors capable of detecting these reduced signal magnetic fields.
- Conventionally, one well known type of sensor for reproduction heads is the magneto-resistive (MR) sensor employing the magneto-resistive effect. The MR sensor is of two types: an anisotropic magneto-resistive (AMR) film employing an anisotropic magneto-resistive effect, and a giant magneto-resistive (GMR) film which is a multi-layered structure.
- A so-called spin-valve structure employing four basic layers is commonly used for the GMR film. The four layers of the spin-valve structure are an anti-ferromagnetic layer, a fixed magnetic layer, a non-magnetic metallic layer and a free magnetic layer.
- Many proposals have been put forward to improve this basic structure, involving mainly improvements in the magnetic materials used and in their combination as well as improvements in the number of layers. However, the size of the signal magnetic fields from the ever more densely recorded magnetic recording medium continues to decrease at a rapid rate, such that mere improvements to the materials and structure of the MR sensor described above are unable to keep pace, that is, are unable to guarantee the level of sensitivity required to reproduce accurately the information recorded on the magnetic recording medium.
- Accordingly, it is an object of the present invention to provide a new and useful magnetic detector in which the above-described disadvantage is eliminated.
- The above-described object of the present invention is achieved by a magnetic sensor that senses an external magnetic field using a spin-filtered sensor current flowing through a non-magnetic layer.
- According to this aspect of the invention, the use of a spin-filtered sensor current flowing through a non-magnetic layer provides a magnetic sensor with improved sensitivity.
- Additionally, the above-described object of the present invention is also achieved by the magnetic sensor as described above, further having:
- a pair of ferromagnetic bodies provided on the non-magnetic layer and positioned parallel to an axis of magnetization of each of the ferromagnetic bodies; and
- a power source that uses the ferromagnetic bodies as electrodes to supply the sensor current.
- Additionally, the above-described object of the present invention is also achieved by the magnetic sensor as described above, wherein:
- a ferromagnetic film is provided on the non-magnetic layer; and
- an axis of magnetization of the ferromagnetic layer is formed either parallel to or opposite to a direction of electron spin of the sensor current.
- Additionally, the above-described object of the present invention is also achieved by the magnetic sensor as described above, wherein the ferromagnetic layer is formed as a free layer constituting either an anisotropic magneto-resistive film or a giant magneto-resistive film.
- Additionally, the above-described object of the present invention is also achieved by the magnetic sensor as described above, wherein:
- the non-magnetic layer is formed of a semiconductor material; and
- the axis of magnetization of one of the pair of ferromagnetic bodies changes so as to detect an external magnetic field.
- Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.
- FIGS. 1A and 1B are schematic diagrams illustrating a basic structure of an MR sensor adapting the present invention;
- FIG. 2 is a diagram illustrating the operating principles of a conventional sensor employing a GMR structure, and specifically, changes in a resistance of a magnetic layer in response to changes in direction of an external magnetic field;
- FIG. 3 is a diagram illustrating an operation of an MR sensor employing the magnetic sensor according to the present invention, and specifically, changes in a resistance of a magnetic layer in response to changes in direction of an external magnetic field;
- FIG. 4 is a schematic diagram showing a basic structure of a spin filter;
- FIG. 5 is a diagram showing a magnetic sensor according to a first embodiment of the present invention;
- FIG. 6 is a diagram showing a magnetic sensor according to a second embodiment of the present invention;
- FIG. 7 is a diagram showing a magnetic sensor according to a third embodiment of the present invention;
- FIGS. 8A and 8B are diagrams illustrating an operation by which the magnetic sensor shown in FIG. 7 detects a magnetic field;
- FIG. 9 is a lateral cross-sectional view of a magnetic recording and/or reproduction device employing the magnetic sensor according to the present invention; and
- FIG. 10 is a diagram showing a plan view of the magnetic recording and/or reproduction device shown in FIG. 9.
- A description will now be given of embodiments of the present invention, with reference to the accompanying drawings. It should be noted that identical or corresponding elements in the embodiments are given identical or corresponding reference numbers in all drawings, with detailed descriptions of such elements given once and thereafter omitted.
- Generally, the magnetic sensor according to the present invention represents a new structure as compared to the conventional magnetic sensors using AMR or GMR structures. That is, the direction of magnetization of the ferromagnetic layers is set to be either parallel to or opposite to the spin of the electrons that make up the sensor current that flows through a non-magnetic layer. The direction of magnetization of one of the ferromagnetic layers then rotates when exposed to a signal magnetic field (external magnetic field) from the magnetic recording medium being read. When the direction of magnetization of the ferromagnetic layer is opposite to the spin orientation of the electrons, the magnetic resistance is at its strongest. When the direction of magnetization of the ferromagnetic layer is parallel to the spin orientation of the electrons, the magnetic resistance is at its weakest. This changing Magnetic Resistance Ratio (MRR) is greater than that of conventional MR sensors, and accordingly, the magnetic sensor of the present invention has greater sensitivity than the conventional MR sensors.
- The magnetic sensor according to the present invention uses either changes in magnetic resistance or else switches a semiconductor material on and off to sense signal magnetic fields (external magnetic fields) from a recording medium.
- A description will first be given of an MR sensor in which changes in magnetic resistance are used to detect changes in magnetic field. In this case, the basic structure of the magnetic sensor used in order to detect the signal magnetic fields from the magnetic recording medium involves a ferromagnetic layer and a non-magnetic layer. By maintaining a predetermined relation between the axis of magnetization of the ferromagnetic layer and the direction of spin of the electrons that form the sensor current flowing through the non-magnetic layer, the signal magnetic field emanating from the recording medium can be detected with a high degree of sensitivity.
- FIGS. 1A and 1B are schematic diagrams illustrating a basic structure of an MR sensor according to the present invention. In FIG. 1A, the direction of magnetization of the ferromagnetic layer and the direction of spin of the electrons of the sensor current flowing through the non-magnetic layer are parallel, whereas in FIG. 1B the two directions are opposed.
- In the state depicted in FIG. 1A, the direction of magnetization of the
ferromagnetic layer 1 is upward, with theelectrons 5 that form the sensor current flowing from bottom to top. At this time, the movement ofelectrons 5 through thenon-magnetic layer 3 is controlled so that the spin of the electrons is also toward the top of the diagram, as inspin electrons 4A. The method by which this spin control is accomplished will be explained later. In any case, the direction of magnetization of theferromagnetic layer 1 and the direction of spin of theelectrons 4A is parallel, such that any dispersion along the boundary between theferromagnetic layer 1 and thenon-magnetic layer 3 is minimal. Accordingly, a magnetic resistance R in the state depicted in FIG. 1A is a minimum value RS. - By contrast, the state shown in FIG. 1B is the opposite of the state shown in FIG. 1A. The direction of magnetization of the
ferromagnetic layer 1 is upward, and theelectrons 5 that form the sense current flow from bottom to top as is the case in FIG. 1A, but the direction of spin of theelectrons 5 within thenon-magnetic layer 3 is downward. - In the state shown in FIG. 1B, the direction of
magnetization 2 of theferromagnetic layer 1 and the spin direction of theelectrons 4B are opposed, so the dispersion at the boundary between theferromagnetic layer 1 and thenon-magnetic layer 2 increases. Accordingly, the magnetic resistance R of the state shown in FIG. 1B is a maximum value RL. - The MR sensor of the present invention uses the states shown in1A and 1B above to sense a signal magnetic field from the magnetic recording medium. In other words, by rotating the direction of
magnetization 2 of theferromagnetic layer 1 according to the signal magnetic field emanating from the magnetic recording medium to achieve the states shown in FIGS. 1A and 1B above, the MRR can be increased and thus detection sensitivity improved. - The above-described MRR can be defined using the following formula, by which the MRR is calculated using both the maximum magnetic resistance value RL obtained when the
magnetization direction 2 of theferromagnetic layer 1 and the direction of thespin electron 4B are opposed as well as the minimum magnetic resistance value RS obtained when themagnetization direction 2 of theferromagnetic layer 1 and the direction of thespin electron 4B are parallel: - MRR=(RL−RS)/RL=1−RS/RL (1)
- Here, a description will be provided of how the MR sensor of the present invention provides an MRR calculated as per the above formula (1) that is greater than that which the conventional MR sensor can provide.
- FIG. 2 is a diagram illustrating the operating principles of a conventional MR sensor employing a GMR structure, and specifically, changes in a resistance of a magnetic layer in response to changes in direction of an external magnetic field.
- As shown in FIG. 2, the
conventional GMR structure 10 includes, from bottom up, a freemagnetic layer 11, anon-magnetic layer 12 and a fixedmagnetic layer 13. It should be noted that theactual GMR structure 10 also has an anti-ferromagnetic layer, a bias layer, and so forth, although in this diagram only those layers that affect changes in the magnetic resistance are included. - In the
conventional GMR structure 10, the sensor current that flows through thenon-magnetic layer 12 is not subjected to forces that would control the spin of the electrons and hence is not in a spin-filtered state. Accordingly, electrons with an upward spin orientation and a downward spin orientation are mixed together and each behaves independently. - As a result, as shown in FIG. 2(a), in which the direction of magnetization of the free
magnetic layer 11 and the direction of magnetization of the fixedmagnetic layer 13 are opposed, theelectrons 15, depending on their direction of spin, either encounter a small resistance RS at a boundary of the freemagnetic layer 11 and a large resistance RL at a boundary layer of the fixedmagnetic layer 13, or conversely, encounter a large resistance RL at the boundary of the freemagnetic layer 11 and a small resistance RS at the fixedmagnetic layer 13. (It should be noted that in FIG. 2 theGMR structure 10 is shown as being on its side, unlike in FIGS. 1A and 1B, so the spin orientation is shown as horizontal instead of vertical.) - Additionally, as shown in (b) of FIG. 2, when the direction of magnetization of the free
magnetic layer 11 and the fixedmagnetic layer 13 are parallel, theelectrons 15 that form the sense current, depending on their spin direction, either acquire a small resistance RS at the boundary of the fixedmagnetic layer 13 and a small resistance at the boundary of the freemagnetic layer 11, or they encounter a large resistance RL at the boundary of the fixedmagnetic layer 13 and a large resistance RL at the boundary of the freemagnetic layer 11. - As described above, with the conventional MR sensor using the conventional GMR structure, there is no attempt to control the spin of the electrons inside the non-magnetic layer. As a result, there are two types of resistance states regardless of whether the directions of magnetization of the free
magnetic layer 11 and the fixedmagnetic layer 13 are parallel or opposed, and it is these states which determine the resistance change values. - However, as described above, what is shown in2(a) above is a state in which the direction of magnetization of the free
magnetized layer 11 and the direction of magnetization of the fixedmagnetized layer 13 are opposed, with the magnetic resistance R shown in the upper part of FIG. 2 at a maximum value Ro. The magnetic resistance R of theGMR structure 10 at this time can be ascertained using the equivalent circuit (c) shown below (a). That is, the maximum magnetic resistance Ro shown in 2(a) can be obtained by this formula: Ro=(RL+RS)/2. - Additionally, as described above, what is shown in2(b) is a state in which the direction of magnetization of the free
magnetized layer 11 and the direction of magnetization of the fixedmagnetized layer 13 are parallel, with the magnetic resistance R shown in the upper part of FIG. 2 at a minimum value Rp. The magnetic resistance R of theGMR structure 10 at this time can be ascertained using the equivalent circuit (d) shown below (b). That is, the minimum magnetic resistance Rp shown in 2(b) can be obtained by this formula: Rp=2RL·RS(RL+RS). - Then, the MRR of the conventional MR sensor using the
GMR structure 10 shown in FIG. 2 can be obtained in the same way as with formula (1) by using the following formula (2): - MRR=(Ro−Rp)/Ro=1−4RL·RS(RL+RS)2 (2)
- Here, the MRR of the conventional GMR structure is approximately 10 percent, so by substituting 0.1 for the MRR in formula (2) above and solving the quadratic equation, we obtain RS/RL=0.52 Then, by substituting RS/RL=0.52 into formula (1) described above for the magnetic sensor of the present invention, we obtain an MRR of 48 percent. Accordingly, the MRR shows an approximate fivefold increase over the conventional model, and if used as the magnetic sensor in a magnetic head would clearly be able to sense signal magnetic fields with a high degree of sensitivity.
- Next, in contrast to the MR sensor employing the conventional GMR structure shown in FIG. 2, a description will be given of an MR sensor employing a GMR structure according to the present invention, with reference initially to FIG. 3.
- FIG. 3 is a diagram illustrating an operation of an MR sensor employing a GMR structure according to the present invention, and specifically, changes in resistance of a magnetic layer in response to changes in direction of an external magnetic field.
- As shown in FIG. 3, a
GMR 20 according to the present invention also includes, from bottom up, a freemagnetic layer 21, anonmagnetic layer 22 and a fixedmagnetic layer 23. However, unlike the conventional arrangement described above, theGMR 20 shown in FIG. 3 gives the electrons of the sensor current flowing inside the non-magnetic layer 22 a right-hand spin. - In the GMR structure according to the present invention, the electron spin is controlled so as to be of one direction only, so that the two types of magnetic resistance states for each of the conditions shown as (a) and (b) in FIG. 2 in the conventional arrangement do not arise but, instead, only one such resistance state exists for each of the two conditions shown. In other words, in the state shown as (a) in the middle of FIG. 3 on the left side, in which a direction of magnetization of a free
magnetic layer 21 and a direction of magnetization of a fixedmagnetic layer 23 are opposed, the boundary of the fixedmagnetic layer 23 with thenon-magnetic layer 22 acquires a small resistance RS and only a small resistance RS, and, simultaneously, the boundary of the freemagnetic layer 21 acquires a large resistance RL and only a large resistance RL. Additionally, in the state shown as (b) in the middle of FIG. 3 on the right side, in which the direction of magnetization of the freemagnetic layer 21 and the direction of magnetization of the fixedmagnetic layer 23 are parallel, the boundary of the freemagnetic layer 21 with thenon-magnetic layer 22 acquires a small resistance RS and only a small resistance RS, and the boundary of the fixedmagnetic layer 23 acquires a large resistance RL and only a large resistance RL. - Thus, the MR sensor shown in FIG. 3 forms only a single resistance state for each of the conditions shown in (a) and (b) of FIG. 3. The maximum MRR of the
GMR structure 20 can be obtained by reference to the equivalent circuit (c) given below (a) in FIG. 3, such that Ro=RL+RS. Similarly, the minimum MRR of theGMR structure 20 can be obtained by reference to the equivalent circuit (d) given below (b), such that Rp1=2Rs. If then the MRR is expressed in terms of formulas such as (1) and (2) above, then - MRR=(Ro−Rp1)/Ro=1−2Rs/(RL+RS) (3)
- Assuming as described above that the conventional GMR structure has an MRR of 0.1 and therefore an RS/RL=0.52, then substituting that RS/RL value into formula (3) above yields an MRR of 31%. Accordingly, the present invention approximately triples the MRR of an MR sensor using a GMR structure as described above, and is thus capable of being employed as the magnetic sensor in a reproduction head. As will be appreciated by those of ordinary skill the art, the
GMR 20 depicted in FIG. 3 can be constructed by converting the twoferromagnetic layers 1 shown in FIG. 1 into the freemagnetic layer 21 of FIG. 3 and by converting thenon-magnetic layer 3 into thenon-magnetic layer 22. - FIG. 4 is a schematic diagram showing a basic structure of a spin filter, employed for the purpose of filtering the spin of the electrons that form the sensor current that flows through the non-magnetic layer.
- As shown in FIG. 4, a pair of ferromagnetic bodies are disposed one at each end of a
non-magnetic layer 31. Theferromagnetic bodies - The
non-magnetic layer 31 can be made of some electrically conductive non-magnetic material such as aluminum, copper, chromium or some alloy of these. Additionally, the ferromagnetic bodies can be formed of a conductive ferromagnetic material selected from among iron, cobalt, nickel or an alloy of these. Attaching apower source 35 to theferromagnetic bodies - When, as shown in FIG. 4, the axes of magnetization of the
ferromagnetic bodies non-magnetic layer 31 between theferromagnetic bodies power source 35. Such a configuration is disclosed for example by Johnson and Silsbee in Phys. Rev. B 37, 5326 (1988), though no application of the principle is suggested. The inventors confirm that an embodiment of the present invention can be achieved using the above-described spin filter 30 basic structure, in which ferromagnetic layers are contacted with anon-magnetic layer 31. - A description will now be given of further embodiments of the present invention, with reference to the accompanying drawings.
- FIG. 5 is a diagram showing a magnetic sensor according to a first embodiment of the present invention.
- The
MR sensor 40 according to the first embodiment is a simple structure, in which anAMR structure 41 adjoins a bottom surface of the spin filter 30. TheAMR structure 41 may be made of the conventional permalloy or Sendust. The axis ofmagnetization 42 of theAMR structure 41 is set so as to be either parallel to or opposed to the direction of spin of the electrons of thenon-magnetic layer 31. When exposed to an external signal magnetic field Hsig the direction ofmagnetization 42 of theAMR structure 41 rotates, detecting magnetically recorded information as changes in magnetic resistance. The two-layer MR sensor of the present embodiment owes its improved sensitivity to a fivefold increase in MRR as compared to the conventional MR sensor described above. - The above-described
MR sensor 40 can be manufactured by commonly known thin film technologies, such as, for example, spattering, development using resist masks, and etching methods. The relatively simple structure of the present embodiment, in which a pair of ferromagnetic bodies are formed atop two layers, makes it possible to produce a highly sensitive MR sensor easily. - FIG. 6 is a diagram showing a magnetic sensor according to a second embodiment of the present invention.
- As shown in FIG. 6, an
MR sensor 50 employs a spin-valve structure on a GMR structure. The spin valve structure is a multilayer structure employing a free magnetic layer, a non-magnetic layer, a fixed magnetic layer and an antimagnetic layer. The free magnetic layer and the non-magnetic layer, as described above, are designed to control the electron spin by means of the spin filter 30 described above. - The spin valve
type MR sensor 50 of the second embodiment has a freemagnetic layer 51 on top of thenon-magnetic layer 31A, and, below thenon-magnetic layer 31, a fixedmagnetic layer 52 and an anti-ferromagnetic layer 53 for pinning the fixedmagnetic layer 52. - The above-described spin-valve structure can be formed using conventional thin film technology. The direction of
magnetization 54 of the freemagnetic layer 51 is set to be either parallel to or opposed to the direction of spin of the electrons of thenon-magnetic layer 31A. When exposed to an external signal magnetic field Hsig, the direction ofmagnetization 54 of the freemagnetic layer 51 rotates, detecting magnetically recorded information as changes in magnetic resistance. The MR sensor using the spin-valve structure shown in the second embodiment described above owes its improved sensitivity to the threefold increase in MRR as compared to the conventional MR sensor described above with reference to FIG. 3. - FIG. 7 is a diagram showing a magnetic sensor according to a third embodiment of the present invention.
- As described above, the first and second embodiments used changes in magnetic resistance arising from the relation between the direction of magnetization of the ferromagnetic layers and the direction of spin of the electrons that form the sensor current that flows through the non-magnetic layer in order to detect an external magnetic field. The third embodiment is an FET-type magnetic sensor, in which the non-magnetic layer is formed of a semiconductor material and which detects the presence of an external magnetic field by switching ON and OFF.
- The
magnetic sensor 60 has a structure like that of the spin filter 30 shown in FIG. 4.Ferromagnetic bodies non-magnetic layer 61 and function as electrodes. The axes of magnetization of theferromagnetic bodies - As described above, the non-magnetic layer is made of a semiconductor material, for example indium aluminum arsenide or indium gallium arsenide, so that when an electric current is supplied to the
ferromagnetic bodies power source 35, as shown in FIG. 7 a spin-filtered sensor current flows through the non-magnetic layer. It should be noted that the principle of a spin-filtered FET is disclosed for example in S. Datra and B. Das, Appl. Phys. Lett. 56 665 (1990), though no mention is made of the applications of such a structure. - In the magnetic sensor according to the third embodiment of the present invention, the spin-filtered FET is used to detect the signal magnetic field emanating from the magnetic recording medium, the operation of which is described with reference to FIGS. 8A and 8B.
- FIGS. 8A and 8B are diagrams illustrating an operation by which the magnetic sensor shown in FIG. 7 detects a magnetic field.
- In both FIGS. 8A and 8B, the above-described
magnetic sensor 60 is disposed perpendicular to a magnetic recording medium which, in this case, is ahard disk 70. FIG. 8A shows detection at a position at which adjacent magnetizations recorded on the surface of the disk come together, and FIG. 8B shows detection at a position at which adjacent magnetizations recorded on the surface of the disk face away from each other. - In FIG. 8A, the direction of the signal magnetic field emanating from the
hard disk 70 and the direction of magnetization of theferromagnetic body 62 are parallel, the spin-filtered sensor current shown in FIG. 7 flows from theferromagnetic body 62 to theferromagnetic body 63, and the semiconductor turns ON. Conversely, in FIG. 8B, the direction of the signal magnetic field emanating from thehard disk 70 and the initial direction of magnetization of theferromagnetic body 62 are opposed, thus causing the magnetization direction of theferromagnetic body 62 to invert so as to become parallel with the direction of the signal magnetic field. As a result, a state in which the sensor current shown in FIG. 7 flows cannot be maintained, theferromagnetic body 62 and theferromagnetic body 63 become electrically insulated from each other and the semiconductor turn OFF. Accordingly, in the third embodiment of the present invention the magnetic sensor uses the switching effect of a semiconductor to detect the external magnetic field. - As can be appreciated by those skilled in the art, the
magnetic sensor 60 can be manufactured using conventional semiconductor production technology or thin film technology. Theferromagnetic bodies ferromagnetic bodies ferromagnetic body 62 must be capable of rotating upon contact with a signal magnetic field while the direction of magnetization of theferromagnetic body 63 must remain fixed in a single direction. - A description will now be given of a magnetic recording and/or reproduction device employing the magnetic sensor described above as a reproduction head, with reference to FIGS. 9 and 10.
- FIG. 9 is a lateral cross-sectional view of a magnetic recording and/or reproduction apparatus (hereinafter magnetic recording/reproduction apparatus) employing the magnetic sensor according to the present invention. FIG. 10 is a diagram showing a plan view of the magnetic recording/reproduction apparatus shown in FIG. 9. The reproduction head used in the magnetic recording/reproduction apparatus employs a spin-filtered sensor current to detect information recorded on a magnetic recording medium.
- As shown in FIGS. 9 and 10, the magnetic recording/reproduction apparatus comprises a
housing 113 and, inside thehousing 113, amotor 114, ahub 115, a plurality ofmagnetic recording media 116, a plurality of recording/reproduction heads 117, a plurality ofsuspensions 118, and a plurality ofarms 119 andactuator units 120. - The
recording media 116 are mounted on thehub 115, which is in turn rotated by themotor 114. Each of the recording/reproduction heads 117 is a compound head consisting of a reproduction head shown in any one of FIGS. 5, 6 and 7 as well as an inductive type recording head. Each recording/reproduction head 117 is mounted at a tip of acorresponding arm 119 via thesuspension 118. Eacharm 119 is driven by anactuator unit 120. The basic structure of the magnetic recording/reproduction apparatus as such is well known and so a detailed description thereof will be omitted. Moreover, the number ofmagnetic recording media 116 is not limited to three but may be 1, 2, or 4 or more such media. Additionally, the types of magnetic recording media need not be limited to the magnetic disks used here. - The above description is provided in order to enable any person skilled in the art to make and use the invention and sets forth the best mode contemplated by the inventors of carrying out the invention.
- The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from, the scope and spirit of the present invention.
- The present application is based on
- Japanese Priority Application No. 2000-175863, filed on Jun. 12, 2000, the contents of which are hereby incorporated by reference.
Claims (11)
1. A magnetic sensor that senses an external magnetic field using a spin-filtered sensor current flowing through a non-magnetic layer.
2. The magnetic sensor as claimed in claim 1 , further comprising:
a pair of ferromagnetic bodies provided on the non-magnetic layer and positioned parallel to an axis of magnetization of each of the ferromagnetic bodies; and
a power source that uses the ferromagnetic bodies as electrodes to supply the sensor current.
3. The magnetic sensor as claimed in claim 1 , wherein:
a ferromagnetic film is provided on the non-magnetic layer; and
an axis of magnetization of the ferromagnetic layer is formed either parallel to or opposite to a direction of electron spin of the sensor current.
4. The magnetic sensor as claimed in claim 3, wherein the ferromagnetic layer is formed as a free layer constituting either an anisotropic magneto-resistive film or a giant magneto-resistive film.
5. The magnetic sensor as claimed in claim 4 , wherein the giant magneto-resistive film constitutes a spin-valve structure.
6. The magnetic sensor as claimed in claim 4 , wherein the non-magnetic layer is formed from a material selected from a group consisting of aluminum, copper, chromium, or an alloy of these metals.
7. The magnetic sensor as claimed in claim 2 , wherein:
the non-magnetic layer is formed of a semiconductor material; and
the axis of magnetization of one of the pair of ferromagnetic bodies changes so as to detect an external magnetic field.
8. The magnetic sensor as claimed in claim 7 , wherein the semiconductor material is indium aluminum arsenide.
9. The magnetic sensor as claimed in claim 7 , wherein the semiconductor material is indium gallium arsenide.
10. The magnetic sensor as claimed in claim 1 , wherein the ferromagnetic body is formed from a material selected from a group consisting of iron, cobalt, nickel, or an alloy of these metals.
11. A device for magnetically recording and reproducing information to and from a recording medium, the magnetic head unit comprising a magnetic sensor that senses an external magnetic field using a spin-filtered sensor current flowing through a non-magnetic layer.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/736,015 US20040131888A1 (en) | 2000-06-12 | 2003-12-15 | Magnetic sensor |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2000-175863 | 2000-06-12 | ||
JP2000175863A JP3604617B2 (en) | 2000-06-12 | 2000-06-12 | Magnetic sensing element |
US09/799,949 US6700761B2 (en) | 2000-06-12 | 2001-03-06 | Magnetic sensor |
US10/736,015 US20040131888A1 (en) | 2000-06-12 | 2003-12-15 | Magnetic sensor |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/799,949 Division US6700761B2 (en) | 2000-06-12 | 2001-03-06 | Magnetic sensor |
Publications (1)
Publication Number | Publication Date |
---|---|
US20040131888A1 true US20040131888A1 (en) | 2004-07-08 |
Family
ID=18677670
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/799,949 Expired - Fee Related US6700761B2 (en) | 2000-06-12 | 2001-03-06 | Magnetic sensor |
US10/736,015 Abandoned US20040131888A1 (en) | 2000-06-12 | 2003-12-15 | Magnetic sensor |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/799,949 Expired - Fee Related US6700761B2 (en) | 2000-06-12 | 2001-03-06 | Magnetic sensor |
Country Status (2)
Country | Link |
---|---|
US (2) | US6700761B2 (en) |
JP (1) | JP3604617B2 (en) |
Families Citing this family (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3604617B2 (en) * | 2000-06-12 | 2004-12-22 | 富士通株式会社 | Magnetic sensing element |
US6781801B2 (en) * | 2001-08-10 | 2004-08-24 | Seagate Technology Llc | Tunneling magnetoresistive sensor with spin polarized current injection |
JP3673250B2 (en) * | 2002-09-30 | 2005-07-20 | 株式会社東芝 | Magnetoresistive element and reproducing head |
JP4714918B2 (en) * | 2002-11-29 | 2011-07-06 | 独立行政法人科学技術振興機構 | Spin injection device and magnetic device using spin injection device |
US7035059B2 (en) * | 2003-07-18 | 2006-04-25 | Hitachi Global Storage Technologies, Netherland B.V. | Head with self-pinned structure having pinned layer extending beyond track edges of the free layer |
JP4469570B2 (en) | 2003-07-24 | 2010-05-26 | 株式会社東芝 | Magnetoresistive element, magnetic head, and magnetic recording / reproducing apparatus |
JP2005251342A (en) * | 2004-03-08 | 2005-09-15 | Tdk Corp | Magnetic head, head suspension assembly and magnetic disk unit |
JP4756868B2 (en) * | 2005-01-31 | 2011-08-24 | キヤノン株式会社 | Detection method |
US7522380B2 (en) * | 2005-06-14 | 2009-04-21 | Seagate Technology Llc | Head to disc interface tunneling giant magnetoresistive sensor |
EP1830410A1 (en) * | 2006-02-24 | 2007-09-05 | Hitachi, Ltd. | Single-charge tunnelling device |
US20090050999A1 (en) * | 2007-08-21 | 2009-02-26 | Western Lights Semiconductor Corp. | Apparatus for storing electrical energy |
US8174260B2 (en) * | 2008-08-26 | 2012-05-08 | Infineon Technologies Ag | Integrated circuit with magnetic material magnetically coupled to magneto-resistive sensing element |
US8525514B2 (en) * | 2010-03-19 | 2013-09-03 | Memsic, Inc. | Magnetometer |
CN104584416B (en) | 2012-08-09 | 2017-05-03 | 国立研究开发法人科学技术振兴机构 | Spin motor and spin rotary member |
US9099119B2 (en) * | 2013-02-11 | 2015-08-04 | HGST Netherlands B.V. | Magnetic read sensor using spin hall effect |
US20150287426A1 (en) * | 2014-04-07 | 2015-10-08 | HGST Netherlands B.V. | Magnetic read head having spin hall effect layer |
US9633678B2 (en) * | 2015-09-29 | 2017-04-25 | Seagate Technology Llc | Data reader with spin filter |
Citations (24)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5390061A (en) * | 1990-06-08 | 1995-02-14 | Hitachi, Ltd. | Multilayer magnetoresistance effect-type magnetic head |
US5416353A (en) * | 1992-09-11 | 1995-05-16 | Kabushiki Kaisha Toshiba | Netoresistance effect element |
US5422571A (en) * | 1993-02-08 | 1995-06-06 | International Business Machines Corporation | Magnetoresistive spin valve sensor having a nonmagnetic back layer |
US5432373A (en) * | 1992-12-15 | 1995-07-11 | Bell Communications Research, Inc. | Magnetic spin transistor |
US5463516A (en) * | 1992-06-23 | 1995-10-31 | Thomson-Csf | Magnetoresistive transducer or magnetic read head including a layer of composite material including conducting magnetic particles in an insulating material |
US5565695A (en) * | 1995-04-21 | 1996-10-15 | Johnson; Mark B. | Magnetic spin transistor hybrid circuit element |
US5629549A (en) * | 1995-04-21 | 1997-05-13 | Johnson; Mark B. | Magnetic spin transistor device, logic gate & method of operation |
US5654566A (en) * | 1995-04-21 | 1997-08-05 | Johnson; Mark B. | Magnetic spin injected field effect transistor and method of operation |
US5691865A (en) * | 1994-02-21 | 1997-11-25 | U.S. Philips Corporation | Magnetic device and method for locally controllably altering magnetization direction |
US5773156A (en) * | 1995-01-26 | 1998-06-30 | Kabushiki Kaisha Toshiba | Magnetoresistance effect element |
US6064552A (en) * | 1997-03-18 | 2000-05-16 | Kabushiki Kaisha Toshiba | Magnetoresistive head having magnetic yoke and giant magnetoresistive element such that a first electrode is formed on the giant magnetoresistive element which in turn is formed on the magnetic yoke which acts as a second electrode |
US6069820A (en) * | 1998-02-20 | 2000-05-30 | Kabushiki Kaisha Toshiba | Spin dependent conduction device |
US6104275A (en) * | 1996-09-20 | 2000-08-15 | Sanyo Electric Co., Ltd. | Magnetoresistive element |
US6114056A (en) * | 1997-05-09 | 2000-09-05 | Kabushiki Kaisha Toshiba | Magnetic element, and magnetic head and magnetic memory device using thereof |
US6130814A (en) * | 1998-07-28 | 2000-10-10 | International Business Machines Corporation | Current-induced magnetic switching device and memory including the same |
US6178112B1 (en) * | 1998-05-13 | 2001-01-23 | Sony Corporation | Element exploiting magnetic material and addressing method therefor |
US6249453B1 (en) * | 2000-04-18 | 2001-06-19 | The University Of Chicago | Voltage controlled spintronic devices for logic applications |
US6285581B1 (en) * | 1999-12-13 | 2001-09-04 | Motorola, Inc. | MRAM having semiconductor device integrated therein |
US6365286B1 (en) * | 1998-09-11 | 2002-04-02 | Kabushiki Kaisha Toshiba | Magnetic element, magnetic memory device, magnetoresistance effect head, and magnetic storage system |
US6381171B1 (en) * | 1999-05-19 | 2002-04-30 | Kabushiki Kaisha Toshiba | Magnetic element, magnetic read head, magnetic storage device, magnetic memory device |
US6387549B1 (en) * | 1998-06-30 | 2002-05-14 | Nec Corporation | Magnetic sensor |
US6480365B1 (en) * | 1999-12-09 | 2002-11-12 | International Business Machines Corporation | Spin valve transistor using a magnetic tunnel junction |
US6700761B2 (en) * | 2000-06-12 | 2004-03-02 | Fujitsu Limited | Magnetic sensor |
US6833980B1 (en) * | 1999-05-10 | 2004-12-21 | Hitachi, Ltd. | Magnetoelectric device |
Family Cites Families (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH05266431A (en) * | 1992-03-18 | 1993-10-15 | Fujitsu Ltd | Magneto-resistance effect type head |
JP3207094B2 (en) | 1995-08-21 | 2001-09-10 | 松下電器産業株式会社 | Magnetoresistance effect element and memory element |
JPH09106913A (en) | 1995-10-13 | 1997-04-22 | Matsushita Electric Ind Co Ltd | Magnetoelectric transducer |
JPH09162460A (en) * | 1995-12-07 | 1997-06-20 | Matsushita Electric Ind Co Ltd | Magnetoresistive effect device and magnetoresistive effect head |
JPH09214016A (en) * | 1996-02-02 | 1997-08-15 | Fujitsu Ltd | Magnetism-sensitive semiconductor element and magnetic head using the same |
US5764567A (en) | 1996-11-27 | 1998-06-09 | International Business Machines Corporation | Magnetic tunnel junction device with nonferromagnetic interface layer for improved magnetic field response |
FR2748843B1 (en) * | 1996-05-15 | 1998-07-17 | Silmag Sa | MAGNETIC HEAD WITH SEMICONDUCTOR FIELD DETECTOR PLACED UNDER THE GAP |
JPH09307156A (en) | 1996-05-15 | 1997-11-28 | Sanyo Electric Co Ltd | Magnetroresistance device |
US5801984A (en) * | 1996-11-27 | 1998-09-01 | International Business Machines Corporation | Magnetic tunnel junction device with ferromagnetic multilayer having fixed magnetic moment |
JP2000504503A (en) * | 1996-12-02 | 2000-04-11 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | Horizontal magnetoelectric device using quasi-two-dimensional electron gas |
JP3206582B2 (en) * | 1998-01-27 | 2001-09-10 | 松下電器産業株式会社 | Spin polarization element |
-
2000
- 2000-06-12 JP JP2000175863A patent/JP3604617B2/en not_active Expired - Fee Related
-
2001
- 2001-03-06 US US09/799,949 patent/US6700761B2/en not_active Expired - Fee Related
-
2003
- 2003-12-15 US US10/736,015 patent/US20040131888A1/en not_active Abandoned
Patent Citations (24)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5390061A (en) * | 1990-06-08 | 1995-02-14 | Hitachi, Ltd. | Multilayer magnetoresistance effect-type magnetic head |
US5463516A (en) * | 1992-06-23 | 1995-10-31 | Thomson-Csf | Magnetoresistive transducer or magnetic read head including a layer of composite material including conducting magnetic particles in an insulating material |
US5416353A (en) * | 1992-09-11 | 1995-05-16 | Kabushiki Kaisha Toshiba | Netoresistance effect element |
US5432373A (en) * | 1992-12-15 | 1995-07-11 | Bell Communications Research, Inc. | Magnetic spin transistor |
US5422571A (en) * | 1993-02-08 | 1995-06-06 | International Business Machines Corporation | Magnetoresistive spin valve sensor having a nonmagnetic back layer |
US5691865A (en) * | 1994-02-21 | 1997-11-25 | U.S. Philips Corporation | Magnetic device and method for locally controllably altering magnetization direction |
US5773156A (en) * | 1995-01-26 | 1998-06-30 | Kabushiki Kaisha Toshiba | Magnetoresistance effect element |
US5565695A (en) * | 1995-04-21 | 1996-10-15 | Johnson; Mark B. | Magnetic spin transistor hybrid circuit element |
US5629549A (en) * | 1995-04-21 | 1997-05-13 | Johnson; Mark B. | Magnetic spin transistor device, logic gate & method of operation |
US5654566A (en) * | 1995-04-21 | 1997-08-05 | Johnson; Mark B. | Magnetic spin injected field effect transistor and method of operation |
US6104275A (en) * | 1996-09-20 | 2000-08-15 | Sanyo Electric Co., Ltd. | Magnetoresistive element |
US6064552A (en) * | 1997-03-18 | 2000-05-16 | Kabushiki Kaisha Toshiba | Magnetoresistive head having magnetic yoke and giant magnetoresistive element such that a first electrode is formed on the giant magnetoresistive element which in turn is formed on the magnetic yoke which acts as a second electrode |
US6114056A (en) * | 1997-05-09 | 2000-09-05 | Kabushiki Kaisha Toshiba | Magnetic element, and magnetic head and magnetic memory device using thereof |
US6069820A (en) * | 1998-02-20 | 2000-05-30 | Kabushiki Kaisha Toshiba | Spin dependent conduction device |
US6178112B1 (en) * | 1998-05-13 | 2001-01-23 | Sony Corporation | Element exploiting magnetic material and addressing method therefor |
US6387549B1 (en) * | 1998-06-30 | 2002-05-14 | Nec Corporation | Magnetic sensor |
US6130814A (en) * | 1998-07-28 | 2000-10-10 | International Business Machines Corporation | Current-induced magnetic switching device and memory including the same |
US6365286B1 (en) * | 1998-09-11 | 2002-04-02 | Kabushiki Kaisha Toshiba | Magnetic element, magnetic memory device, magnetoresistance effect head, and magnetic storage system |
US6833980B1 (en) * | 1999-05-10 | 2004-12-21 | Hitachi, Ltd. | Magnetoelectric device |
US6381171B1 (en) * | 1999-05-19 | 2002-04-30 | Kabushiki Kaisha Toshiba | Magnetic element, magnetic read head, magnetic storage device, magnetic memory device |
US6480365B1 (en) * | 1999-12-09 | 2002-11-12 | International Business Machines Corporation | Spin valve transistor using a magnetic tunnel junction |
US6285581B1 (en) * | 1999-12-13 | 2001-09-04 | Motorola, Inc. | MRAM having semiconductor device integrated therein |
US6249453B1 (en) * | 2000-04-18 | 2001-06-19 | The University Of Chicago | Voltage controlled spintronic devices for logic applications |
US6700761B2 (en) * | 2000-06-12 | 2004-03-02 | Fujitsu Limited | Magnetic sensor |
Also Published As
Publication number | Publication date |
---|---|
JP2001358379A (en) | 2001-12-26 |
JP3604617B2 (en) | 2004-12-22 |
US6700761B2 (en) | 2004-03-02 |
US20010053052A1 (en) | 2001-12-20 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
KR100336733B1 (en) | Low moment/high coercivity pinned layer for magnetic tunnel junction sensors | |
US6392850B1 (en) | Magnetoresistive transducer having a common magnetic bias using assertive and complementary signals | |
US6473275B1 (en) | Dual hybrid magnetic tunnel junction/giant magnetoresistive sensor | |
US6833982B2 (en) | Magnetic tunnel junction sensor with a free layer biased by longitudinal layers interfacing top surfaces of free layer extensions which extend beyond an active region of the sensor | |
US6219212B1 (en) | Magnetic tunnel junction head structure with insulating antiferromagnetic layer | |
US7116530B2 (en) | Thin differential spin valve sensor having both pinned and self pinned structures for reduced difficulty in AFM layer polarity setting | |
US5768071A (en) | Spin valve sensor with improved magnetic stability of the pinned layer | |
US6621664B1 (en) | Perpendicular recording head having integrated read and write portions | |
US7567411B2 (en) | Magnetoresistive sensor | |
US6700761B2 (en) | Magnetic sensor | |
JPH10116404A (en) | Self-bias magnetic refluctance spin bulb sensor, head including the same, and magnetic disk including the same | |
US20090097166A1 (en) | Magnetoresistive element, magnetic head and magnetic recording/reproducing apparatus | |
US6788502B1 (en) | Co-Fe supermalloy free layer for magnetic tunnel junction heads | |
US6801409B2 (en) | Read head shield having improved stability | |
KR100389598B1 (en) | Magnetoresistive sensor, magnetoresistive head, and magnetic recording/reproducing apparatus | |
US7038889B2 (en) | Method and apparatus for enhanced dual spin valve giant magnetoresistance effects having second spin valve self-pinned composite layer | |
US20020141120A1 (en) | Bias structure for magnetic tunnel junction magnetoresistive sensor | |
US6327123B1 (en) | Magnetic head employing magnetoresistive sensor and magnetic storage and retrieval system | |
KR100553489B1 (en) | Spin-valve magnetoresistance effect head, composite magnetic head comprising the same, and magnetoresistance recorded medium drive | |
US7180714B2 (en) | Apparatus for providing a ballistic magnetoresistive sensor in a current perpendicular-to-plane mode | |
US6515838B1 (en) | Biasing correction for simple GMR head | |
US6704176B2 (en) | Spin valve sensor | |
US20080118778A1 (en) | Magnetoresistive reproducing magnetic head and magnetic recording apparatus utilizing the head | |
JP2000182224A (en) | Spin valve reading sensor having high heat stability and its manufacture |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |