WO1990009658A1

WO1990009658A1 - Thin-film magnetic head with two magnetic poles separated by a narrow gap for vertical recording

Info

Publication number: WO1990009658A1
Application number: PCT/EP1989/001331
Authority: WO
Inventors: Heinrich Diepers
Original assignee: Siemens Aktiengesellschaft
Priority date: 1989-02-13
Filing date: 1989-11-07
Publication date: 1990-08-23

Abstract

The magnetic head (2) contains a conducting element (5) which conducts the magnetic flux and which has two magnetic arms (6, 7) that delimit a narrow gap (20). Each magnetic arm has a magnetic pole (P1, P2) at a pole tip (8, 9) and each has a magnetic reinforcing layer (6b, 7b) outside the region of the pole tips. According to the invention, one magnetic arm (6) is provided with an additional pole layer (15) adjacent to the gap (20), and made of a material whose saturation magnetization (Ms') and/or relative permability (ν') are/is greater than those of the material of the other parts of the magnetic conducting body (5).

Description

Thin-film magnetic head with two magnetic poles separated by a narrow gap for vertical recording

The invention relates to a thin-film magnetic head for vertical (vertical) recording with a magnetic flux guiding the magnetic flux, applied to a non-magnetic substrate, which has a ring-like shape and contains two magnetic legs, each of which has at least one Have a magnetic layer and form a magnetic pole on a pole tip facing vertically to be agglomerated recording medium, - the magnetic poles of which, viewed in the (relative) direction of movement of the head, are arranged one behind the other and separated from one another by a gap with a small gap width which is further apart from the gap width Have space-defining limb parts through which the windings of a read / write coil winding extend and which are each provided with a magnetic reinforcement layer outside the area of their pole tips, these reinforcement layers corresponding T Form the outer sides of the magnetic guide body.

Such a thin-film magnetic head is described in EP-B-0 185 289.

The principle of a vertical (vertical) magnetization for storing data in corresponding, in particular plate-shaped recording media is generally known. Thin-film magnetic heads designed for this type of magnetization generally have one for guiding the magnetic flux Guide body made of magnetizable material, which, in particular with two magnetic legs, can have a shape similar to a ring shape. These magnetic legs form magnetic poles on their pole tips facing the recording medium, which are arranged one behind the other as seen in the relative direction of movement of the head with respect to the recording medium, a narrow gap being formed between the pole tips. Outside the area of these pole tips, the magnetic legs delimit a space which is expanded accordingly due to an increase in the mutual distance between the magnetic legs. The conductors of at least one read / write coil winding extend through this intermediate space.

The magnetic head known from the aforementioned EP-B also shows a corresponding structure. In addition to at least one magnetic layer forming the respective magnetic pole, each of the magnetic legs of this magnetic head also contains a magnetic reinforcement layer outside the region of the pole tips. These reinforcing layers, which serve to improve the flow guidance or to reduce the magnetic resistance in the magnetic guide body, are arranged in such a way that they essentially form the outer sides of the magnetic guide body. This guide body is constructed on the back of a non-magnetic substrate using thin-film technology, the substrate being designed as a missile so that it can be guided aerodynamically over the plate-shaped recording medium.

In particular, such thin-film magnetic heads for vertical magnetization require high recording densities of, for example, more than 50 kfci (kilo flux changes per inch). The magnetic heads must therefore be able to write particularly sharp magnetization transitions and be able to read with very narrow head fields. The object of the present invention is now to design the thin-film magnetic head of the type mentioned at the outset in such a way that it can produce narrow write errors with a steeper edge and in particular also narrow read fields and thus a corresponding increase in the upper write fields frequency and a high resolution when reading.

This object is achieved according to the invention in that the magnetic limb, which is seen in the (relative) direction of movement, is provided with an additional pole layer which delimits the gap on one side and is made of a material whose saturation magnetization and / or its relative permeability are respectively greater are / is the saturation magnetization or relative permeability of the at least one material of the other parts of the magnetic guide body.

In the magnetic head according to the invention, the magnetic flux brought up via the leading magnetic leg at its pole tips is then concentrated on the additional pole formed by the additional pole layer with its higher permeability. The higher saturation magnetization of this additional pole means that this pole also saturates later than the immediately adjacent areas of the magnetic pole of the adjacent magnetic leg. This is associated in particular with the advantage that the magnetic field profile to be reproduced in a diagram of the magnetic head according to the invention or of its leading magnetic leg provided with the additional pole becomes relatively steep and narrow. This consideration applies to both the case of writing and the case of reading. Consequently, the measures according to the invention also lead to a narrower reading pulse. Associated with this is also advantageously a reduction in the so-called bit shift, ie the spatial or temporal shift between a written magnetization transition and a read transition (compare, for example, "IEEE Trans.Magn.", Vol. MAG-19, No .5, Sept. 1983, pages 1617-1619). The measures according to the invention can can be used particularly advantageously for magnetic heads according to the vertical magnetization principle.

Advantageous refinements of the magnetic head according to the invention emerge from the subclaims.

The invention is explained in more detail below with reference to the drawing. 1 of the drawing schematically shows an embodiment of a magnetic head according to the invention. 2 shows a detail of a corresponding magnetic head. FIG. 3 shows a diagram of a magnetic field component to be generated by this magnetic head. FIGS. 4 and 5 show further design options for the magnetic head according to FIG. 2. Parts that correspond to one another in the figures are provided with the same reference numerals.

In the case of the thin-film magnetic head for writing and reading, which is only partially illustrated as a longitudinal section in FIG. 1, it is assumed that ring-head-like embodiments known per se with a layered structure for the principle of longitudinal (horizontal) or in particular vertical (vertical) magnetization. The head, generally designated 2 in the figure, is formed using thin-film technology on a substrate 3, which can be designed as a missile in a known manner and is not further developed in the figure. A body 3a made of TiC-A ^ O- is advantageously used as the substrate. Since this material is electrically conductive due to the TiC component, the substrate 3 must additionally be provided with an insulation layer 3b made of, for example, A1 ₂ 0 ₃ . Instead of TiC, AlN in particular can also be used as the substrate material. The substrate 3 and therefore the magnetic head 2 are to be guided aerodynamically along a track at a low flight altitude relative to a recording medium known per se and corresponding to the intended magnetization principle. This relative to the head Movement of the recording medium, for example under this rotating recording medium, is indicated by an arrow marked with an arrow.

The triple magnetic head 2 has a guide body 5 guiding the magnetic flux with two magnetic legs 6 and 7. These magnetic legs each contain at least one magnetic layer 6a and 7a, which each form a magnetic pole P1 and P2 on their pole tips 8 and 9 facing the recording medium. Outside the regions occupied by the pole tips 8 and 9, each magnetic leg is reinforced with an additional, relatively thick magnetic layer 6b or 7b. These additional layers are advantageously used to reduce the magnetic resistance in the magnetic guide body 5 and are also used for a possibly aimed Asy metering of the field profile of the writing field of the head. The two reinforcement layers 6b and 7b are advantageously arranged such that they lie on the outer sides of the magnetic guide body. The reinforcement layer 6b, which is associated with the magnetic leg leading in relation to the direction of movement v, is located in a waπ-like recess 11. This recess can advantageously be incorporated into the insulating cover layer 3b of the substrate 3 and with the reinforcement layer 6b be filled in that the surface 12 of the reinforcing layer 6o facing the magnetic layer 6a lies in a common plane E together with the non-recessed surface 13 of the cover layer 3b.

In a central area of the ring-head-like magnetic guide body 5, the distance between the two magnetic legs 6 and 7 is widened in that the rearward (trailing) magnetic leg 7 with respect to the direction of movement v in this area is at a greater distance w from the front, even trained and the substrate i 3 facing magnetic leg 6 leads. Outside this extended guide body region, the magnetic leg 7 is attached to the magnetic leg 6 in a known manner on the side of the guide body facing away from the recording medium, so

5 that then the ring head-like shape of the guide body 5 results. The space 16 thus present between the two magnetic legs 6 and 7 in the extended guide body region extends at least one single-layer or multi-layer coil winding 17 with which both the writing and the reading function can be carried out. If necessary, separate windings must also be provided for this. The entire magnetic guide body 5 is covered on its outside with a hard, non-magnetic protective layer 18, for example made of A1 ₂ 0 ₃ .

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The pole region of a head corresponding to the magnetic head 2 according to FIG. 1 is illustrated in more detail in FIG. 2. As can be seen from this figure, an additional pole layer 15 is to be provided according to the invention, which is the pole tip

20 one of the two magnetic legs reinforced and forms an additional pole P '. Advantageously, the leading magnetic leg 6 facing the substrate 3 is provided with this additional pole layer 15. The pole layer, the longitudinal, i.e. Thickness d to be measured in the direction of movement v is generally one

25 ert has between 0.2 μ and 1.5 μm, lies against the side of the magnet leg 6 facing the opposite magnet leg 7. Their vertical extension a is advantageously at least as large as the corresponding extension b of the part of the magnetic layer 6a which is the pole tip 8

30 forms and is not reinforced by means of the reinforcing layer 6b. A gap 20 with an advantageously small longitudinal width g then remains between the pole layer 15 forming the additional pole P ¹ and the pole tip 9 of the magnetic leg 7 forming the pole P2. This width g lies in

35 generally in the range of a few tenths of a micrometer, preferably in the range below 0.5 μm, for example around 0.1 μm. The magnetic layers 6a, 6b, 7a and 7b of the magnetic guide body 5 advantageously consist of the same or, if appropriate, also of different known soft agnetic materials. Suitable materials for this are, for example, special NiFe alloys such as Permalloy or CoZr or CoHf. These materials have a predetermined Sättigungsmagne- tisieruπg Ms of example, at least 800 kA per meter and a relative permeability μ of at least 500. In contrast, according to the invention is intended for the additional pole layer 15, a material can be selected whose saturation magnetization Ms ¹ and / or its relative permeability μ ¹ are / are comparatively larger than the saturation magnetization Ms or as the relative permeability μ. It is to be regarded as advantageous if the saturation magnetization Ms ^{1 is selected to be} greater than Ms in the first place. Suitable materials for the pole layer 15 are, for example, CoNb alloys with additions of Fe or Zr or Mo or Cr or Ru. CoHf or CoZr or CoFe alloys with additions of Ta or Pt or Pd (cf. for example EP-A-0 192 161) can also be used. In addition, known alloys, which contain at least some of the components Fe, Si, Al, Ge and Ga, also meet the requirements with regard to high saturation magnetization Ms ¹ and high relative permeability μ '. In general, it can be assumed that materials are particularly suitable if their saturation magnetization Ms ^{1 is} at least 1.5 times the saturation magnetization Ms. The relative permeability μ ¹ need not necessarily be increased to the corresponding degree or not at all in relation to the relative permeability μ ¹ . On the other hand, if, according to the invention, primarily an increased relative permeability μ ^{1 is to be} provided, then it is advantageous if the following applies: μ ¹ ^ 1.5 - μ. With such a choice of material, the specific configuration of the magnetic layer 6a and the pole layer 15 assigned to it can be carried out in such a way that no magnetic saturation in a transition area A of the magnetic flux outlined by the dashed line from the magnetic layer 6a to the pole layer 15 occurs with increasing current in a coil winding 17 (see FIG. 1). Magnetic saturation should advantageously only occur at the pole tips. This can be ensured by choosing the vertical extension a of the pole layer 15 to be equal to or greater than the corresponding extension of the non-reinforced part of the magnetic layer 6a. The extent of this non-reinforced part is determined by the distance e of the tip of the reinforcing layer 6b facing the recording medium from the plane of the pole face of the magnetic pole P ¹ / P ¹ .

This measure, namely by avoiding premature saturation in the transition region A between the magnetic layer 6a and the pole layer 15, also ensures that short circuits in the magnetic flux between the magnetic layers 6a and 7a are reduced. These river short-circuits are indicated in FIG. 2 by an arrow 21. A reduction of such flux short circuits is also advantageously promoted that the reinforcing layer 6b is arranged on the outside of the magnetic guide body 5 and thus relatively far away from the magnetic layer 7a.

As with magnetic heads for vertical magnetization in general, with the magnetic head according to the invention the effective gap width is larger than the geometrical width g of the gap 20. The effective gap width is namely essentially determined by the flux density distribution or by the position of the maxi a Field strengths in the pole Pl / P ¹ on the one hand and the pole P2 on the other hand, as well as by the magnetic properties of the recording medium, particularly when using a soft magnetic base under the storage layer. The effective gap width is advantageously reduced by the formation of the additional pole P ¹ ; This results in correspondingly short pulse lengths, so that large bit densities can be read with the magnetic head according to the invention. This applies in particular if narrow magnetization transitions with a steep profile are written into the recording medium, so that the head determines the resolution with its effective gap width.

In Fig. 3, the field relationships generated when writing a thin-film magnetic head according to the invention are compared to that of a known magnetic head in a diagram. In this diagram, only the y components of the magnetic fields H generated by the magnetic heads are indicated as a function of the extension x of the respective head pointing in the direction of movement v. The field strength curve denoted by Hy (dashed line) results for a magnetic head, as can be seen from EP-B-0 232 505 (cf. there in particular FIG. 2). This known magnetic head has no additional pole layer like a head according to the invention. In contrast, the field strength curve Hy '(solid line) is obtained when the known magnetic head is redesigned according to the invention. As can be clearly seen when comparing the two curves Hy and Hy ', the field strength curve Hy'd of the magnetic head according to the invention advantageously shows a steeper course of its flank, which is to be assigned to the trailing (writing) edge of the head. A magnetic head designed according to the invention can therefore write correspondingly sharper magnetization transitions. In addition, since the field strength curve Hy 'has a very narrow maximum, the written magnetization transitions are scanned accordingly in high resolution when reading. According to the embodiment selected above for FIGS. 1 to 3, it was assumed that the magnetic head according to the invention has a leading magnetic leg 6 with at least one magnetic layer 6a, the end of which facing the recording medium together with the corresponding end of the additional pole layer 15 Magnetic pole Pl / P ^{1 forms} with a pole face lying in a common plane. If necessary, however, the at least one magnetic layer of this magnetic leg can be configured to be vertically shortened compared to the additional pole layer; ie, in this case it no longer extends to the plane of the pole face of this leg, so that only the additional pole layer 15 then defines the pole face of the magnetic pole. A corresponding exemplary embodiment can be seen from the section in FIG. 4, for which a representation corresponding to FIG. 2 has been selected. In this figure, the vertically shortened magnetic layer is designated 6c.

This magnetic layer 6c can optionally also be shortened to such an extent that its end facing the recording medium coincides with the end of the magnetic reinforcement layer 6b assigned to it. This special case is indicated in FIG. 5, starting from the embodiment according to FIG. 4. As can be seen from this figure, the shortened magnetic layer and the associated reinforcement layer can then be formed by a common layer 6d. In this figure it is further illustrated that in a magnetic head according to the invention the pole layer 15 generally does not necessarily have to reach all the way to the end of a magnetic reinforcement layer, but rather extends a little in the area delimited by the two magnetic legs 6 and 7 Space 16 can extend.

Claims

1. Thin-film magnetic head for vertical (vertical) recording with a magnetic flux which guides the magnetic flux and is applied to a non-magnetic substrate

Guide body, which has a ring-like shape and contains two magnetic legs, each having at least one magnetic layer and forming a magnetic pole on a pole tip facing a recording medium to be magnetized vertically, - whose magnetic poles in the (relative) direction of movement of the

Seen head one behind the other and separated by a gap, t with a small gap width, which, compared to the gap width, have spaced-apart limb parts, through which the turns of a read / write coil winding extend, and which lie outside the area their Polspitzeπ are each provided with a magnetic reinforcing layer, wherein these reinforcing layers form corresponding parts of the outside of the magnetic guide body, characterized in that the magnetic leg (6) leading in (relative) direction of movement (v) has a gap (20 ) is provided on one side with an additional pole layer (15) made of a material whose saturation magnetization (Ms ¹ ) and / or whose relative permeability (μ ¹ ) is / is greater than the saturation magnetization (Ms) or relative permeability - did (μ) of the at least one material of the remaining T hurry of the magnetic guide body (5).

2. Magnetic head according to claim 1, dadurchge ¬ indicates that the substrate (3) facing Magπetscheπkel (6) with the additional pole layer (15) is provided.

3. Magnetic head according to claim 1 or 2, since d. urchge ¬ indicates that the at least one magnetic layer (6a) of the leading magnetic leg (6) together with the additional pole layer (15) together form the magnetic pole (Pl / P ¹ ) of this leg.

4. Magnetic head according to claim 1 or 2, dadurchge ¬ indicates that the at least one Magnet¬ layer (6c) of the leading magnetic leg (6) with respect to the additional pole layer (15) is shortened vertically so that this pole layer (15) only the magnetic pole (P ¹ ) of this leg forms. (Fig. 4)

5. Magnetic head according to claim 4, so that the shortened magnetic layer and the associated reinforcing layer are formed by a common layer (6d). (Fig. 5)

6. Magnetic head according to one of claims 1 to 5, since - characterized in that the vertical extension (a) of the additional pole layer (15) is at least as large as the distance (e) of the reinforcing layer (6b) from the pole face of the magnetic pole (Pl / P 'or P ¹ ) of the associated magnetic leg (6).

7. Magnetic head according to one of claims 1 to 6, so that the thickness (d) of the additional pole layer (15) to be measured in the direction of movement (v) of the additional pole layer (15) is between 0.2 μm and 1.5 μm.

8. Magnetic head according to one of claims 1 to 7, since ¬ characterized in that the saturation magnetization (Ms ¹ ) of the material of the additional pole layer (15) at least 1.5 times the saturation magnetization (Ms) of the material of the other parts of the magnetic guide body (5).

9. Magnetic head according to one of claims 1 to 8, d a ¬ d u r c h g e k e n n z e i c h n e t that the saturation magnetization (Ms) of the other parts of the magnetic guide body (5) is at least 800 kA / m.

10. Magnetic head according to one of claims 1 to 9, since ¬ characterized in that the relative permeability (μ ¹ ) of the material of the additional pole layer (15) at least 1.5 times the relative permeability (μ) of the material of the other parts of the magnetic guide body (5) is.

11. Magnetic head according to one of claims 1 to 10, d a ¬ d u r c h g e k e n n z e i c h n e t that the relative permeability (μ) of the material of the other parts of the magnetic guide body (5) is at least 500.

12. Magnetic head according to one of claims 1 to 11, d a ¬ d u r c h g e k e n n z e i c h n e t that a CoNb or a CoHf or a CoZr or a CoFe alloy is provided as the material for the additional pole layer (15).

13. Magnetic head according to one of claims 1 to 12, since - characterized in that the magnetic reinforcement layer (6b) of the magnetic leg (6) facing the substrate (3) in a corresponding recess (11) of the substrate (3rd ) is arranged.