JP2002092828A - Magnetoresistive effect type thin film magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce instability of output fluctuation, asymmetrical fluctuation, Barkhausen noise and the like without incurring the reduction of reproducing output by stabilizing a magnetic domain structure in a free layer of a MR sensor part. SOLUTION: In a magnetoresistive effect type thin film magnetic head provided with a lower magnetic shield, a magnetoresistive effect sensor 61 for reproduction, hard magnetic layers 64 and 65 disposed at both end parts of the sensor opposite to each other and stabilizing the magnetic domain structure of the sensor, an upper magnetic shield, an upper magnetic core for recording and a magnetizing coil for recording operation, the magnetoresistive effect sensor for reproduction has a gradient leaned to the negative side for a magnetic distortion constant from the center part to the both end parts of the sensor. Then the magnetoresistive effect type thin film magnetic head has a magnetic distortion controlling layer 62 for controlling the magnetic distortion constant of the sensor and an underground layer 63 for controlling the magnetic characteristics of the hard magnetic layers between the sensor and the hard magnetic layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined read / write type thin film magnetic head used in a magnetic disk drive or the like.

[0002]

2. Description of the Related Art In recent years, with the increase in recording density of magnetic disk devices and the like, instead of an inductive magnetic head for both recording and reproduction, a conventional inductive magnetic head for recording has been used, and a read / write operation of a recording has a magnetoresistance effect. MR) sensor using a read / write combined thin film magnetic head (hereinafter referred to as M
R head). In recent years, in particular, a ferromagnetic layer (free layer) that rotates in accordance with an external signal magnetic field, a nonmagnetic conductive layer for passing a current, a ferromagnetic material and an antiferromagnetic layer are stacked, and a cup is formed at an interface between them. A giant magnetoresistive (GMR) film typified by a spin valve film composed of a multilayer film in which a ferromagnetic layer (fixed layer) in which the magnetization of a ferromagnetic material is fixed in one direction by a ring and a multilayer film in which layers are sequentially stacked is used. A GMR head, and a TMR in which an insulating layer typified by alumina or the like is used in place of the nonmagnetic conductive layer, and a greater magnetoresistance change can be selected by the tunnel effect.
Membrane heads are promising as next-generation heads.

In a GMR head typified by a spin valve film, a reproduced waveform disorder such as output fluctuation, asymmetry fluctuation and Barkhausen noise is often observed.
This is considered to occur because the magnetic domain structure of the free layer is unstable. In order to prevent this, permanent magnets are arranged at both ends of the free layer, and the magnetization of the free layer is aligned in one direction by the generated magnetic field, thereby realizing a stable magnetic domain structure and suppressing output fluctuation and Barkhausen noise. be able to.

Further, an antiferromagnetic layer is stacked outside the read track width of the free layer, and the magnetization of the free layer is stabilized in one direction by exchange coupling at the interface, thereby causing output fluctuation, asymmetry fluctuation, Barkhausen fluctuation and the like. It has been thought that noise can be suppressed. Generally, the former is called a hard bias type, and the latter is an exchange coupling bias type (Exchange).
Bias type).

However, in the hard bias type magnetic head, output fluctuations occur only by stabilizing the magnetization state of the free layer by the magnetic field of the permanent magnets disposed at both ends of the free layer.
It has been found that asymmetry fluctuation and Barkhausen noise cannot be suppressed.

In order to suppress output fluctuation, asymmetry fluctuation and Barkhausen noise, it is necessary to control the magnetic characteristics of the free layer. In an actual magnetic head, anisotropic stress is applied to the GMR sensor portion at the time of processing into a slider chip, so it is necessary to control the magnetostriction constant of the free layer to an appropriate value. According to a study and research of the present inventors, the output fluctuation, in order to suppress the asymmetry variation and Barkhausen noise of the magnetostriction constant 0-10 - found that it is necessary to control the degree (× 10 ⁷⁾ Conversely, when the magnetostriction constant is made positive, the output of the head increases, but the output fluctuation and Barkhausen noise increase, and the result is that the asymmetry of the output waveform greatly varies.

[0007] When the magnetostriction constant of the free layer is changed, the frequency of occurrence of output fluctuation, asymmetry fluctuation and Barkhausen noise changes because the magnetic domain structure of the free layer, particularly the magnetization state at the free layer end, is closely related. There is a relationship. According to the investigations and researches of the present inventors, when the magnetostriction constant is made positive, the magnetization direction at the end of the free layer becomes unstable due to the residual stress of the head element structure, and the magnetization that should originally be directed to the track width direction is obtained. Are easily oriented in the depth direction of the head, and the magnetization state of the entire free layer does not become one direction from the starting point and becomes unstable, which causes output fluctuation, asymmetry fluctuation and Barkhausen noise.

When the magnetostriction constant is negative, the magnetization of the free layer tends to be oriented in the track width direction, and the magnetization state becomes stable. Ideally, the magnetization state becomes a single magnetic domain state, thereby causing output fluctuation, asymmetry fluctuation and Barkhausen noise. Is considered to be able to be suppressed. However, when the magnetostriction constant is increased to a negative value, the magnetic anisotropy in the track width direction increases, and the rotation of the magnetization of the free layer hardly occurs, which causes a reduction in the read output of the head.

As described above, it is necessary to control the magnetostriction constant of the free layer to a negative value in order to suppress output fluctuations, asymmetry fluctuations and Barkhausen noise, and to reduce asymmetry fluctuations in output waveforms. The output of the head could not be increased.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to suppress output fluctuation, asymmetry fluctuation and Barkhausen noise without lowering the reproduction output of the head. .

[0011]

In order to solve the above problems, the present invention mainly employs the following configuration.

A lower magnetic shield, a magnetoresistive sensor for reproduction, a hard magnetic layer disposed opposite to both ends of the sensor to stabilize a magnetic domain structure of the sensor, an upper magnetic shield, and an upper magnetic recording layer; In a magneto-resistance effect type thin-film magnetic head including a magnetic core and a recording operation exciting coil, a magneto-resistance effect (MR) sensor for reproduction has a negative magnetostriction constant from a central portion to both end portions of the sensor. A magnetoresistive thin-film magnetic head having a gradient deviated to

A lower magnetic shield; a magnetoresistive sensor for reproduction; a hard magnetic layer disposed opposite to both ends of the sensor to stabilize a magnetic domain structure of the sensor; An upper magnetic core for
And a magnetic characteristic of the hard magnetic layer, between the sensor and the hard magnetic layer, for controlling a magnetostriction constant of the sensor. Magnetoresistive thin-film magnetic head having an underlayer for controlling the magnetic field.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetoresistive thin-film magnetic head according to an embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view showing a schematic configuration of a combined read / write thin film magnetic head according to this embodiment.

In FIG. 1, a magnetoresistive thin-film magnetic head includes, for example, a substrate 10, a base film layer 11, a lower magnetic shield layer 12, an insulating layer 13, an MR sensor section 14, a hard bias layer and an electrode layer 15, an upper magnetic layer. Shield layer 1
6, an organic insulating film layer 17, an exciting coil 18, an upper magnetic core 19 for writing, and the like. FIG. 1 differs from the prior art in that the underlying film of the hard bias layer 15 has a multilayer structure.

Conventionally, a permalloy (NiFe) alloy, which is a soft magnetic material, is often used for the free layer. In order to control the magnetostriction constant of the free layer, it is common to change the composition of this permalloy.
e Up to about 20 Wt% is often used.

On the other hand, there is a method of adding an impurity to control the magnetostriction constant. When a metal impurity is added to a permalloy alloy, the magnetostriction constant is often positive. For example, Ni-based alloys of 50 at% or more and Pd of rare metals have an effect of making the magnetostriction constant negative.

In the present invention, if an impurity is added to the permalloy, the magnetostriction constant of the entire film changes, so that a desired effect cannot be obtained. Then, a material serving as an impurity is laminated on the permalloy film as a film, and heat treatment is applied thereto to cause interdiffusion at the interface, thereby controlling the magnetostriction constant of the permalloy film as the free layer. Also, if a desired shape is patterned by using a technique such as photolithography, the magnetostriction constant at an arbitrary position can be controlled.

Next, a description will be given of how the magnetostriction constant changes when various impurities are stacked on the permalloy film as the free layer and heat-treated.

First, FIG. 2 shows a change in magnetostriction constant when a Cr film is laminated on a permalloy film and heat treatment is applied. In this example, it can be seen that the magnetostriction constant of the permalloy film changes to the positive side by the heat treatment. Here, the heat treatment temperature is 230 to 250 ° C., but it is desirable to perform the heat treatment at a temperature of 150 ° C. or more in order to cause interdiffusion at the interface. In the example shown in FIG. 2, it is not appropriate from the viewpoint of the present invention that the magnetostriction constant at the end of the free layer in the track width direction is set on the negative side. In addition,
In FIG. 2, the horizontal axis represents the time when a free layer (NiFe) was formed (deposition) on the substrate, the time when Cr was formed on the free layer, the time when heat treatment was performed at 230 ° C. for 3 hours (3 h), and And the time point of the heat treatment for 9 hours.

FIG. 3 shows a change in magnetostriction constant when a NiCr film is laminated on a permalloy film and heat treatment is applied. In this example, it can be seen that the magnetostriction constant of the permalloy film changes to the negative side by applying the heat treatment. Although the Cr composition is set to 20 at% here, the Cr composition is desirably 50 at% or less in order to make the magnetostriction constant negative. Although the heat treatment temperature is 230 to 250 ° C., it is desirable to perform the heat treatment at a temperature of 150 ° C. or more in order to cause interdiffusion at the interface. In the example shown in FIG. 3, it is appropriate from the viewpoint of the present invention that the magnetostriction constant at the end of the free layer in the track width direction is set on the negative side.

FIG. 4 shows a change in magnetostriction constant when a Pd film is laminated on a permalloy film and heat treatment is applied. In this example, it can be seen that the magnetostriction constant of the permalloy film changes to the negative side by applying the heat treatment. Here, the heat treatment temperature is 23
Although the temperature is set to 0 to 250 ° C., it is desirable to perform the heat treatment at a temperature of 150 ° C. or more in order to cause interdiffusion at the interface. In the example shown in FIG. 4, it can be said that the magnetostriction constant at the end of the free layer in the track width direction is set to the negative side, which is appropriate from the viewpoint of the present invention.

As shown in FIGS. 3 and 4, the magnetostriction constant of the permalloy film can be appropriately set by laminating a NiCr alloy or a Pd film on the permalloy film as a free layer and applying heat treatment. . The value of the magnetostriction constant can be controlled by changing the thickness of the laminated film and the heat treatment time.

FIG. 5 shows an example of a magnetic head having a conventional structure.
51 is an MR sensor unit, 52 is a free layer, 53 is a base film, 5
Reference numeral 4 denotes a hard magnetic layer (permanent magnet). In a conventional hard bias structure, a Co-based permanent magnet, for example, CoC
Any material such as r, CoPt, CoCrPt, or CoCrTa is generally used. However, in order to direct its crystal magnetic anisotropy into the film plane and sufficiently increase the coercive force, Cr, C
Underlayer materials such as rTi and CrW are used to form a hard magnetic layer that stabilizes the magnetic domain of the MR sensor. However, in such a hard bias structure, the free layer is formed by vacuum deposition such as sputtering after the end of the free layer in the track width direction is etched by dry etching such as ion milling. At the end of
The permalloy alloy, which is the free layer, comes into contact with the underlying material.

In this state, if heat treatment is applied during the process, mutual diffusion occurs between the permalloy alloy at the end of the free layer and the hard bias underlayer (Cr), and the magnetostriction constant of the permalloy at the end of the free layer becomes positive. The movement (see the change in the magnetostriction constant shown in FIG. 2) results in an unstable magnetization state at the end of the free layer, which causes output fluctuation, asymmetry fluctuation and Barkhausen noise.

FIG. 6 shows an example in which the multilayer film according to the embodiment of the present invention is applied to a magnetic head. 6, reference numeral 61 denotes a free layer, 62 denotes a magnetostriction control layer (base film 1), 63 denotes a base film 2,
Numeral 64 denotes the base film 3 and numeral 65 denotes a hard magnetic layer (permanent magnet). Under the conventional Cr underlayer (underlayer 3 in FIG. 6), two metal films, that is, underlayer 63 and underlayer 62 are further provided.
Is arranged, and Ni, Pd, or a NiCr alloy, a NiPd alloy,
It is characterized in that one of PdCr alloys is used.

In this state, when a heat treatment during the process is applied, the permalloy alloy at the end of the free layer and Ni of the hard bias,
Interdiffusion occurs between the underlayers 62 of Pd or NiCr alloy, NiPd alloy, or PdCr alloy, and the magnetostriction constant of the permalloy moves in the negative direction at the end of the free layer (see the graphs of FIGS. 3 and 4). As a result, the magnetization state at the end of the free layer becomes stable, and output fluctuation, asymmetry fluctuation and Barkhausen noise can be suppressed (the function and operation of the underlayer 63 will be described later). Here, when a Cr alloy is used, it is desirable that the content of Cr be 50 at% or less in view of a change in magnetostriction constant. Hereinafter, this first underlayer is referred to as a magnetostriction control layer.

On the other hand, FIG. 7 shows the results of the magnetic characteristics (coercive force) when a conventionally used Cr-based Co-based permanent magnet film is conventionally laminated on the magnetostriction control layer. FIG. 7 shows an example in which the hard magnetic layer is composed of a Cr underlayer and a CoCrPt permanent magnet, and this hard magnetic layer is laminated on the NiCr magnetostriction control layer. Thus, C is directly applied to the magnetostriction control layer.
It can be seen that a sufficiently large coercive force cannot be obtained even if a Co-based permanent magnet film as an underlayer is laminated. Even if the Cr film thickness is increased, only about 1000 Oe can be obtained at most.

In order to solve this, a second underlayer (corresponding to the underlayer 63 shown in FIG. 6) is used on the magnetostriction control layer. It is desirable to use a TaW alloy or a TiW alloy for the second underlayer. The composition of these films is preferably a W composition of 20 to 40 at%.

FIG. 8 shows the magnetic properties when a NiCr alloy is used for the magnetostriction control layer, a TaW alloy is used for the second underlayer, and a conventionally used Cr-based Co-based permanent magnet film is further laminated thereon. The result of (coercive force) is shown. From this result, in order to obtain a sufficient coercive force for the permanent magnet, a second underlayer made of a TaW alloy was provided, and the thickness of the underlayer was 6n.
m or more is required.

FIG. 9 shows an example in which the difference in the magnetization state due to the difference in the stress distribution state of the free layer and the magnetostriction constant is calculated by simulation. FIG. 10 is a schematic diagram in which the magnetization state at the end is disturbed. From FIG. 9, if the magnetostriction constant is negative,
The magnetization state in the plane of the free layer is stable, and in such a magnetic domain structure, output fluctuation, asymmetry fluctuation and Barkhausen noise are unlikely to occur, but since the in-plane magnetic anisotropy is large,
The magnetization rotation angle with respect to the same external signal magnetic field becomes smaller, and the read output of the head becomes smaller.

When the magnetostriction constant becomes positive, the magnetization state in the plane of the free layer is disturbed. This indicates that the in-plane magnetic anisotropy is weak from the relationship between the film stress and the magnetostriction constant. Therefore, in such a magnetic domain structure, output fluctuation, asymmetry fluctuation and Barkhausen noise are liable to occur, but since the in-plane magnetic anisotropy is small, the magnetization rotation angle with respect to the same external signal magnetic field becomes large, and the reproduction of the head is performed. The output will be large.

When the magnetostriction constant is positive as shown in FIG. 10, the magnetization state is disturbed at the end of the free layer, and output fluctuations, asymmetry fluctuations and Barkhausen noises are liable to occur starting therefrom.

Accordingly, the present invention provides a head having a large magneto-striction constant at the end portion of the free layer with respect to the magnetostriction constant at the end portion of the free layer, thereby maintaining a large reproduction output of the head and providing a free layer. The basic idea is to eliminate disturbance of the magnetization state at the end. As a specific configuration example of the present invention, the magnetostriction constant at the center of the free layer is a positive value or a value of zero or a negative value near zero, and the magnetostriction constant at the end is a negative value. Can be mentioned. In addition,
In FIGS. 3 and 4, the magnetostriction constant when a free layer is formed on a substrate is a negative value, and this value can be changed depending on the thickness of the free layer and becomes almost zero. The magnetostriction constant can be changed from negative to positive by adding an appropriate impurity. As described above, in the present invention, the magnetostriction constant of the free layer end is given a negative gradient by the magnetostriction control layer with respect to the magnetostriction constant of the free layer. In addition, the reproduction output of the head can be increased without the occurrence of asymmetry fluctuation or Barkhausen noise.

FIG. 11 shows the recording / reproducing characteristics of the head (magnetic head shown in FIG. 5) without using the magnetostriction control layer of the present invention and the magnetic head used (magnetic head shown in FIG. 6). The horizontal axis in FIG. 11 represents the output fluctuation rate, and the vertical axis represents the cumulative frequency indicating the cumulative frequency of the number of occurrences. Comparing heads using other structures and the like with the same structure, the head using the magnetostriction control layer clearly shows superiority in head stability evaluation items such as output fluctuation and asymmetry fluctuation.

As described above, according to the embodiment of the present invention, when forming the hard magnetic layer for controlling the magnetic domain of the free layer, which is disposed at both ends of the free layer of the MR sensor, the magnetostriction control is performed. Layer, an intermediate metal layer, and a hard magnetic layer (including a base film of the hard magnetic layer), and the material of the magnetostriction control layer is interdiffused into the free layer due to heat history during the device process. By controlling the magnetostriction constant at the end to a value different from the magnetostriction constant at the center of the free layer, a free layer having a magnetostriction gradient is realized. This stabilizes the magnetic domain structure at the end of the free layer and suppresses output fluctuation, asymmetry fluctuation, and Barkhausen noise.

[0037]

According to the present invention, it is possible to provide a magnetic head with reduced instability such as output fluctuation, asymmetry fluctuation and Barkhausen noise without reducing the reproduction output.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of a combined read / write thin film magnetic head according to an embodiment of the present invention.

FIG. 2 is a diagram showing a change in magnetostriction constant when a Cr film is laminated on a permalloy film as a free layer and heat treatment is applied.

FIG. 3 shows a permalloy film as a free layer according to the embodiment;
FIG. 9 is a diagram showing a change in magnetostriction constant when an iCr film is laminated and heat treatment is applied.

FIG. 4 is a view showing a Pm-free film of a free layer according to the present embodiment;
It is a figure which shows the change of the magnetostriction constant when a d film | membrane is laminated | stacked and the heat processing is applied.

FIG. 5 is a diagram showing an example of a magnetic head having a conventional structure.

FIG. 6 is a diagram showing a structure of a composite magnetic head according to the embodiment, in which a multilayer film including a hard magnetic layer is laminated at an end of a free layer.

FIG. 7 is a diagram showing the results of magnetic properties (coercive force) when a NiCr alloy is laminated on a magnetostriction control layer and a Co-based permanent magnet film of a Cr underlayer of a conventional structure is laminated thereon.

FIG. 8 shows the magnetic properties when a NiCr alloy is used for a magnetostriction control layer and a TaW alloy is used for a second underlayer according to the present embodiment, and a Co-based permanent magnet film with a Cr underlayer of a conventional structure is further laminated thereon. It is a figure showing a result of a characteristic (coercive force).

FIG. 9 is a diagram showing an example in which a difference in magnetization state due to a difference between a stress distribution state of a free layer and a magnetostriction constant is calculated by simulation.

FIG. 10 is a diagram showing a schematic diagram in which the magnetization state of the free layer end is disturbed.

FIG. 11 is a diagram showing the recording and reproducing of a head using a magnetostriction control layer and a base film according to an embodiment of the present invention and a magnetic head having a conventional structure;
FIG. 9 is a diagram showing a reproduction characteristic result.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 11 Base film layer 12 Lower magnetic shield layer 13 Insulating layer 14 MR sensor part 15 Hard bias layer and electrode layer 16 Upper magnetic shield layer 17 Organic insulating film layer 18 Excitation coil 19 Upper magnetic core for writing 51 MR sensor part 52 Free layer 53 Underlayer 54 Hard magnetic layer (permanent magnet) 55 Electrode film 61 Free layer 62 Magnetostriction control layer (underlayer 1) 63 Underlayer 2 64 Underlayer 3 65 Hard magnetic layer (permanent magnet)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoki Koyama 2880 Kozu, Kozuhara-shi, Kanagawa Prefecture Within Hitachi, Ltd.Storage Systems Division (72) Inventor Shobun Miyamoto 2880 Kozu, Kozu, Odawara-shi, Kanagawa Hitachi, Ltd. Within Storage System Division (72) Inventor Kenji Ishikake 2880 Kozu, Odawara City, Kanagawa Prefecture F-term within Storage Systems Division, Hitachi, Ltd. 2G017 AA10 AB00 AC01 AD55 CB28 5D034 BA03 BA05 BA12 BA21 BB09 BB12 CA04 DA07 5E049 AA07 BA00 BA12 BA16

Claims (6)

[Claims] 1. A lower magnetic shield, a reproducing magnetoresistive sensor, a hard magnetic layer disposed opposite to both ends of the sensor to stabilize a magnetic domain structure of the sensor, an upper magnetic shield, and a recording medium. A magnetoresistive effect type thin-film magnetic head comprising an upper magnetic core for recording and an exciting coil for recording operation, wherein the magnetoresistive sensor for reproduction has a gradient in magnetostriction constant from the center to both ends of the sensor. A magnetoresistive thin-film magnetic head, characterized in that: 2. The magnetoresistive thin-film magnetic head according to claim 1, wherein magnetostriction constants at both end portions of the sensor are set to be more negative than those at a central portion thereof. Thin film magnetic head. 3. A lower magnetic shield, a magnetoresistive sensor for reproduction, a hard magnetic layer disposed opposite to both ends of the sensor to stabilize a magnetic domain structure of the sensor, an upper magnetic shield, and a recording medium. A magnetoresistive thin-film magnetic head comprising: an upper magnetic core for recording; and an exciting coil for recording operation, wherein a magnetostriction control layer for controlling a magnetostriction constant of the sensor is provided between the sensor and the hard magnetic layer. A magnetoresistive thin-film magnetic head comprising a base layer for controlling magnetic properties of a hard magnetic layer. 4. The magnetoresistive thin-film magnetic head according to claim 3, wherein the magnetostriction control layer is made of Ni, Pd, NiCr alloy, NiP.
A magnetoresistive thin-film magnetic head comprising one of a d alloy and a PdCr alloy. 5. The magnetoresistive thin-film magnetic head according to claim 3, wherein said underlayer is made of a TaW alloy or a TiW alloy. 6. The magnetoresistive thin-film magnetic head according to claim 3, wherein the magnetostriction control layer is made of Ni, Pd, NiCr alloy, NiP.
The underlayer is made of a TaW alloy or a TiW alloy, and the hard magnetic layer is made of a Co-based permanent magnet and an underlayer material of Cr, CrTi alloy or CrW alloy. A magnetoresistive thin-film magnetic head characterized in that: