JPH0714120A - Thin-film head with different magnetostriction region - Google Patents

Abstract

PURPOSE: To minimize unsuitable stress-induced domain arrangement and noise in the top end and rear areas of a magnetic pole by setting magnetic distortion constant and thickness of a magnetic layer so that they produce different magnetic distortion degree in the top end area and the rear area of the magnetic pole. CONSTITUTION: An inductive thin film magnetic head comprises yoke 40 which consists of two magnetic pole pieces. One piece consists of two magnetic film layers P1 and P1S, and the other consists of two magnetic film layers P2 and P2S. The layer P1 extends from an end of a rear gap part 42 which abuts an end of a rear area 44 of the yoke 40 to a far end of a magnetic pole top end area 46, and the layer P1S directly abuts the layer P1 and extends from the end of the part 42 virtually only to neighborhood of the area 46. The layer P2 directly abuts the layer P1S in the part 42, separates from the layer P1S in the rest part of the area 44 and approaches the layer P1 for the purpose of defining an exchange gap between the layers P2 and P1. The layer P2S directly abuts the layer P2 and extends virtually over only the same distance as the layer P1S from the part 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic head,
More specifically, it relates to an inductive thin film magnetic head having films with different magnetostriction constants used in different regions of the head to minimize improper stress-induced domain placement and noise in the region.

[0002]

2. Description of the Related Art In a thin film head, the axis along which the magnetization of the film is easy should ideally be perpendicular (that is, lateral) to the direction in which the magnetic flux propagates. This is true if the flux rotation occurs primarily due to the rotation because the magnetization rotation is faster and more static, and not due to domain boundary motion. Although the film grows in a magnetic field and produces the desired lateral inhomogeneity (H _k ), the uniaxial method film stress ▽ σ during assembly is the stress in the magnetic field inhomogeneity (H _stress ). Due to the induced change, noise may be generated especially in the magnetic pole tip region of the head, and there is a possibility that the magnetization may change easily in the axial direction. The stress-induced nonuniformity is H
_It can be expressed as _stress = 3λ ▽ σ / M _s .

Here, λ is the magnetostriction constant, M _s is the saturation magnetization, and λ and M _s are component dependent. Since .sigma. And .lamda. Are difficult to control during the manufacturing process, thin film heads are typically constructed using NiFe compositions with negative magnetostriction constants. The magnetic film is under effective uniaxial stress along the axis of symmetry of the head,
Therefore, the above approach is valid when H _stress is added to H _k . However, during high-density track recording, the thin film head exhibits more complicated stress. When the magnetic film has a single-valued magnetostriction constant λ, the stress causes an unfavorable change in the axial direction in which magnetization is easy, from the lateral direction in the yoke to the longitudinal direction in the magnetic pole and the area behind the head. I have something to do.

US Pat. No. 4,750,072 describes a thin film magnetic head having a magnetic core structure or magnetic yoke structure having a pole tip region and a back region.
The central portion of both regions is made of a magnetic material having a positive magnetostriction constant, and the opposite side surface portions of both regions are made of a magnetic material having a negative magnetostriction constant. The back area has no back gap.

US Pat. No. 4,663,607 uses zero laminar strain for the purpose of eliminating stress changes in magnetic properties using laminar flow with magnetostrictive constants of opposite sign in magnetostrictive (MR) elements. There is a description on a method of providing an MR element with.
All examples include two or more layers of the same thickness, coextensive in area (ie, the same size). Also, in the above patent (column 6, lines 60-64), the above presentation can be used to provide an MR head, but no arrangement for such a head is pointed out or suggested.

[0006]

Even if combined, these above-mentioned depictions are intended to minimize undesired stress-induced domain placement and noise of the head, such as the back gap portion of the back region and the pole tip region. It does not indicate or suggest a thin film magnetic head in which different magnetostriction constants are selected for different regions.

There is a need for thin film magnetic induction heads and a process for making them identical. Here in the process,
Without adding a new step to the head assembly process, it is possible to reduce the effective magnetostriction constant λ and, in particular, to reduce noise caused by stress-induced non-uniform changes in the magnetic anisotropy in the magnetic pole tip region. Allows independent optimization of λ.

[0008]

A thin film magnetic head is composed of a magnetic yoke adjacent to one end which is a back gap portion of a back region and adjacent to the other end which is a magnetic pole tip region.
The yoke has two pole pieces. One magnetic pole piece is composed of a magnetic layer P1 extending from the yoke end to the other end and a layer P.
1 of the magnetic layer P1S that directly contacts the yoke 1 and substantially extends from the yoke end to the end adjacent to the magnetic pole tip region. The other pole piece is the layer P1S at the back gap.
Directly to the P1S in other parts of the back area.
And a magnetic layer P2 that is separated from P1 in the magnetic pole tip region and forms a conversion gap between P1 and P1. The magnetic layer P2S that is in direct contact with the P2 is overlaid in at least a part of the back region.

The layers P1, P1S, P2 and P2S have magnetostriction constants λ ₁ , λ _1s , λ ₂ and λ _2s , thicknesses t ₁ , t _1s , t ₂ and t.
_2s each, chosen to produce different magnetostrictions in the pole tip region and the back region to minimize the effects of noise and differences in stress-induced domain placement in these regions.

In the example presented, t ₁ , t _1s , t ₂ and t _2s are less than 3 microns and therefore P1 is P1S.
In addition, in the region where P2 contacts P2S, the layers P1 and P1 are
The two layers of S and P2 · P2S are each (t ₁ λ ₁ + t _1s λ _1s )
/ (T ₁ + t _1s ) and (t ₂ λ ₂ + t _2s λ _2s ) / (t ₂ + t
_It behaves as a single film layer with an effective magnetostriction constant λ _eff of _2s ).

In the portion composed of the single layers P1 and P2, the magnetostriction constants are λ ₁ and λ ₂ , respectively.

T ₁ and t ₂ are substantially 1 micron, t _1s and t
It is recommended that _2s be substantially 2 microns.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 2 and 3 are yokes 10 of the introductory depiction conventionally used for induction thin film magnetic heads having a negative magnetostriction constant λ. The yoke 10 comprises a pole tip region 12 and a back region 14 having a back gap portion 16 in the region. FIG. 1 is a typical arrangement of magnetized domains 18. FIG. 2 shows the easy axis of the thin film magnetic head magnetization. In FIG. 3, a uniaxial tensor stress component 20 and several compressive stress components 22 are shown.

FIG. 4 shows a two-layer structure 3 showing the basic concept of the present invention.
It is a figure of 0. The two-layer structure 30 has a thickness t ₁ and a magnetostriction constant λ ₁
And a magnetic layer 34 having a thickness t ₂ and a magnetostriction constant λ ₂ .

According to a feature of the invention, the thicknesses t ₁ and t ₂ are 3
Submicron, there is sufficient magnetic coupling between layers 32 and 34. Therefore, the region A having two coupling layers has λ _eff =
It behaves as a single magnetic film having an effective magnetostriction constant λ _{eff that} can be expressed by (t ₁ λ ₁ + t ₂ λ ₂ ) / (t ₁ + t ₂ ).

However, the region B having the single magnetic layer 32 has a magnetostriction constant λ ₁ . This has two advantages: 1. Proper selection of t ₁ , λ ₁ , t ₂ and λ ₂ makes it possible to have two separate and independently selectable values of λ in the two regions A and B. In this way, if the stresses are different in the two regions, it is possible to optimize λ in order to cancel or minimize the stress effect in each region. 2. The magnetic films 32, 34 can be formed using different film deposition devices, so the process variations of the two devices are statistically independent and Gaussian. The process dispersion σ _eff for controlling λ _eff for the two-layer region A is then derived as follows.

[Equation 1]

Where σλ is the dispersion of the single film deposition apparatus, and therefore enhances the process control effectiveness. For example, t
₁ = t2σ _eff t ₁ is reduced by the amount obtained by dividing σλ by route 2.

This basic concept is applied to two different thin film head arrangements, and its application is described below.

As shown in FIG. 5, the induction thin film magnetic head is composed of two magnetic pole pieces, one is a two magnetic film of P1 and P1S, and the other is a yoke 40 composed of two magnetic films of P2 and P2S. To be done.

The layer P1 extends from one end of the yoke to the other. That is, from the end of the back gap portion 42 adjacent to the end of the back region 44 to the far end of the pole tip region 46. The layer P1S is in direct contact with the layer P1 and extends only from the end of the back gap portion 42 to substantially near the end of the pole tip region 46.

The layer P2 is the layer P1 in the back gap portion 42.
It is in direct contact with S and is separated from the layer P1S in the remainder of the back region 44 and is close to the layer P1 in the pole tip region 46 for the purpose of limiting the conversion gap between the two layers. Layer P2
S directly contacts layer P2 and extends from back gap portion 42 by substantially the same distance as layer P1S.

In using the term "substantially" as used hereinafter or in the claims, the exact lengths of P1S and P2S are within the tolerances of the assembly process employing conventional thin film pattern deposition techniques. Considering that there is a difference in.

In this thin-film magnetic head, which is typical of the contents shown in the drawn front view, it is conventional that the layers P1 and P1S have a slightly negative magnetostriction and the layers P2 and P2S have a more negative magnetostriction. Take the way. The reason for this is that layers P2 and P2S
Due to the higher level stress in the middle, the magnetostriction constant, sign and thickness of P1 and P2 are the same, but the layers P1S and P2S
It is due to the fact that they are different from those values of.

As depicted in FIG. 3, a stress profile standard is considered here, and the head has the arrangement shown in FIG. In accordance with the present invention, the pole tip region 46 is made slightly smaller or equal to a slightly positive value λ, while the back region 44, including the back gap portion 42, is maintained at a larger negative absolute value of the head. Stress effects can be eliminated to optimize performance, or at least effective minimization is possible. Negative values of λ in the back region 44 match the tensor high stresses found therein, while λ of near zero or slightly positive value reduces stress effects in the pole tip region 46. Therefore, the intrinsic lateral anisotropy H _k causes a normal orientation of the magnetization there. If the exact magnitude and variability of the stress there is unknown, then λ near zero in the pole tip region 46 is preferred. This design is preferred if the actual magnetic behavior at the back gap portion 42 is within acceptable limits. This arrangement will be sufficient for most applications, as the flux path at the back gap portion 42 extends over a fairly wide range.

In order to counteract the stress effects in the back gap portion 42 at the back region 44, the embodiment shown in FIG. 6 is preferred. This embodiment differs from the embodiment depicted in FIG. 5 in that the layer P2S is substantially from the inner (not outer) end of the back gap portion 42 to substantially the pole tip region 46.
It is up to the edge of. This arrangement of FIG. 6 can be used to provide the back gap portion 42 with a magnetostriction constant that is more negative or actually slightly more positive than the portion of the back region 44 excluding the back gap portion 42. For good write efficiency, the pole tip region 46 should saturate in front of the back gap portion 42. In order to ensure this, the back gap portion has a pole tip region 46 in terms of the thickness reduction due to the lack of the P2S layer in the back gap portion.
Should be at least twice as wide.

Sufficient magnetic coupling is provided by the layers P1, P1S, P2,
Utilization of a normal cleaning process is essential to ensure that it exists between each two layers of P2S. A magnetostriction constant near zero is preferred to optimize λ in the pole tip region 46 and the back gap portion 42, because this constant minimizes the effect of stress changes on head sensitivity. . However, if the stress variations in the subsequent assembly and head processes are different, it is still possible to carry out the optimization using the improved method of the user.

In the implementation of the embodiment of FIGS. 5 and 6, the magnetostriction constant λ and the thickness of each layer are as follows. [Table 1] Layer λ t P1 -1X10 ^-6 1.0 μ P1S -1X10 ^-6 2.0 μ P2 ± 1X10 ^-7 1.0 μ P2S -3X10 ^-6 2.0 μ

In any case, what is essential is that there are no layers with a thickness of 3 microns or more in order to ensure a sufficient magnetic coupling between the layers, so that each layer is as described in connection with FIG. It behaves as a single magnetic film.

[0029]

As described above, according to the present invention, by using the magnetic coupling layers having different magnetostriction constants which reduce the sensitivity of the thin film, the stress induced anisotropy effect which may result in the noise and the performance decrease. On the other hand, by using the high density recording head, the head assembly process can be optimized.

[Brief description of drawings]

FIG. 1 is a systematic design diagram of an induction thin film magnetic head yoke showing a typical arrangement of magnetic domains.

FIG. 2 is a systematic design diagram of an induction thin-film magnetic head yoke showing the axis of easy magnetization.

FIG. 3 is a systematic design diagram of an induction thin film magnetic head yoke showing a uniaxial stress component.

FIG. 4 is a side view of a two-layer structure showing the basic concept of the present invention.

FIG. 5 is a simplified cross-sectional view of a yoke structure of a thin-film magnetic head according to one embodiment of the present invention.

FIG. 6 is a simplified cross-sectional view of a yoke structure of a thin film magnetic head modified according to another embodiment of the present invention.

[Explanation of symbols]

 10 Yoke 12 Pole tip region 14 Back region 16 Back gap part 18 Magnetization domain 22 Compressive stress component 30 Two-layer structure 32 Magnetic layer 34 Magnetic layer 42 Back gap part 44 Back region 46 Pole tip region

Front Page Continuation (72) Inventor Mohamed Toufik Klounbi, USA 95120 San Jose, California, Paso Los Cerritos 6238 (72) Inventor Pokan One United States 95120 California, San Jose, Shadow Brooke Drive 1007

Claims (11)

[Claims] 1. A magnetic yoke having first and second magnetic pole pieces, a first magnetic layer extending from a back gap portion adjacent to one end of the back region to a pole tip region, and contacting the first magnetic layer. The first magnetic pole piece composed of a second magnetic layer extending substantially from the back gap portion to the magnetic pole tip region, and the second magnetic layer only in the back gap portion, and in the magnetic pole tip region, A third magnetic layer, which is distant from the first magnetic layer and forms a conversion gap between the two layers, and a portion of the third magnetic layer are in contact therewith, and extend from the back gap portion to substantially the pole tip region. A fourth magnetic layer, the first magnetic layer being selected to produce different magnetostrictions in the pole tip region and the back region for the purpose of minimizing the effects of each stress induced domain difference and noise in the region. , Second, third and Thin-film magnetic head having a second pole piece having a magnitude and sign of the magnetostriction constant of the fourth magnetic layer. 2. The back region, including the back gap portion, has a negative magnetostriction constant preselected for said purpose to substantially match the stress level in the back gap portion, and the pole tip region there. The magnetic head of claim 1, having a smaller magnetostriction constant near zero to substantially match the stress level. 3. The second and fourth layers are (i) substantially the same width as the first and third layers, and (ii) substantially the magnetic pole tip over the entire back region including the back gap portion. The magnetic head according to claim 1, which extends to the vicinity of the edge of the region. 4. The magnetic head according to claim 1, wherein the fourth layer substantially extends over the back region including the back gap part to near the end of the pole tip region in order to reduce the magnetostriction in the back gap part. 5. The pole tip has a width that is at least twice the width of the pole tip zone and maintains write efficiency despite the reduced thickness of the back gap portion due to the lack of the fourth layer thereat. 5. The magnetic head according to claim 4, which ensures that the area is saturated in front of the back gap portion. 6. A magnetic yoke adjacent to one end of the back gap portion of the back region and the other end of the magnetic pole tip region, the yoke having first and second magnetic pole pieces, the first magnetic pole. The piece is in direct contact with the first magnetic layer P1 extending from the yoke end to the other end thereof, and
A second magnetic layer P1S substantially extending from the yoke end to an end adjacent to the magnetic pole tip region, the second magnetic pole piece being in direct contact with the second layer at the back gap portion, A third magnetic layer P2 that is separated from the second magnetic layer in the other part of the back region, and is slightly separated from the first magnetic layer in the magnetic pole tip region and forms a conversion gap with the first magnetic layer there; A fourth magnetic layer P2S that is in direct contact with the third magnetic layer and is overlaid in at least a portion of the back region, wherein the layers P1, P1S, P2 and P2S have magnetostriction constants λ ₁ , λ _1s , λ ₂ and λ _2s and thicknesses t ₁ , t _1s , t ₂ and t _2s
Respectively, and their values were chosen to produce different magnetostrictions in the pole tip region and the back region in order to minimize the effects of differences in stress-induced domain placement and noise in the region. , A thin film magnetic head. 7. The t ₁ , t _1s , t ₂ and t _2s are less than 3 microns and therefore P1 is P1S and P2 is P2.
In the area that contacts S, 2 of P1, P1S and P2, P2S
Each layer is a single layer having an effective magnetostriction constant λ _eff of (t ₁ λ ₁ + t _1s λ _1s ) / (t ₁ + t _1s ) and (t ₂ λ ₂ + t _2s λ _2s ) / (t ₂ + t _2s ). Acting as a membrane layer, single layers P1 and P
7. The magnetic head according to claim 6, wherein the magnetostriction constants in the region constituted by 2 are λ ₁ and λ ₂ , respectively. 8. The magnetic head of claim 6 wherein t ₁ and t ₂ are substantially 1 micron and t _1s and t _2s are substantially 2 microns. 9. λ ₁ and λ _1s are substantially −1 × 10 ⁻⁶ , λ ₂
Is substantially ± 1 × 10 ⁻⁷ , λ _2s is substantially −3 × 10 ⁻⁶
The magnetic head according to claim 8, wherein 10. A region having a magnetostriction constant λ _x · λ _y and a thickness t _x · _ty and having a layer contact between layers x and y is (t _x
A magnetic structure consisting of a thin film magnetic layer giving an effective magnetostriction constant of λ _x + _ty λ _y ) / (t _x + _ty ). 11. The magnetic structure according to claim 10, wherein the magnetostriction constants are λ _x and λ _y even in a region where the layers x and y are not in multilayer contact.