JPH07107732B2 - Magnetoresistive thin film head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is recorded on a magnetic recording medium using a magnetoresistive effect element (hereinafter referred to as an MR element) to which the magnetoresistive effect of a ferromagnetic thin film is applied. The present invention relates to a magnetoresistive thin film head that detects a signal.

[Conventional technology]

It is known that a magnetoresistive effect type thin film head (hereinafter referred to as an MR head) that applies the magnetoresistive effect of a ferromagnetic thin film has many advantages as compared with a wound type magnetic head which has been widely used conventionally. There is. For example, the MR head receives a signal magnetic field generated from the magnetization pattern recorded on the magnetic recording medium and takes out this as a voltage change based on the resistance change of the MR element. The signal can be reproduced without depending on.
Therefore, the MR head has an advantage that a reproduction signal having a higher output can be obtained than that of the winding type magnetic head when the transfer speed of the magnetic recording medium is low.

A so-called yoke type MR head in which the MR element part is provided away from the tape sliding surface in the conventional MR head, and a yoke serving as a magnetic flux introduction path for guiding the magnetic flux generated in the magnetic recording medium to the MR element part is arranged. (Hereinafter referred to as YMR head), and this YMR head is more effective in improving signal resolution and MR element durability than forming a thin film magnetic head with a single MR element. is there. In recent years, this YMR head has been attracting attention as a fixed head and a reproducing head for digital audio (refer to the 8th Annual Meeting of the Applied Magnetics Society of Japan, 1984, 14PB-11 “Reproduction characteristics of a yoke type MR head”). ).

The conventional YMR head, as shown in FIG. 5 and FIG.
On the substrate 11 for the magnetic head, an insulating layer 12 and an MR element 13 having lead conductors 18, 18 connected to both ends thereof are formed in this order, and on the substrate 11, the insulating layer 12, and the MR element 13. An insulating film 14 for a gap is formed on. Further, on the gap insulating film 14, an upper yoke 16 having an end face in the same plane as the end face of the substrate 11, and an upper yoke 17 facing the upper yoke 16 with a gap therebetween are provided. . These upper yokes 16 and 17 form a magnetic path of a magnetic recording signal detected from the magnetic recording medium 15 such as a magnetic tape. The upper yoke 16, the MR element 13, and the upper yoke 17 are magnetically coupled in this order.

[Problems to be solved by the invention]

However, in the above conventional structure, the output signal obtained from the MR element 13 contains Barkhausen noise due to the discontinuous change in the magnetization inside the MR element 13. Has a problem that it has an extremely bad influence on the output signal processing in the YMR head (The above-mentioned 8th Annual Meeting of the Applied Magnetics Society of Japan (1984) 14PB-11 "Reproduction of yoke type MR head". Characteristic"
reference).

The above-mentioned Barkhausen noise is caused by the discontinuous change in the magnetization inside the MR element 13, but the root cause of the discontinuous change in the magnetization inside the MR element 13 is the MR element. 13 Disturbance of magnetic anisotropy inside (hereinafter referred to as anisotropic dispersion). The cause of this anisotropic dispersion is that, as shown in FIG. 6, during film formation, the MR element 13 exhibits uniaxial anisotropy having an easy axis of magnetization only in the track width direction indicated by KK '. This is because the uniaxial anisotropy is disturbed due to various external factors when the YMR head is completed. The external factors mentioned above are due to the thermal history in the manufacturing process of the YMR head.
That the film itself of the element 13 deteriorates and anisotropic dispersion increases,
In addition, external stress is applied to the film of the MR element 13 and
In the above film, stress-induced magnetic anisotropy is generated by the inverse magnetostrictive effect of the MR element 13 film, and the like.

The external stress applied to the film of the MR element 13 may be a force applied to the MR element 13 as a reaction of the internal stress generated in the gap insulating film 14 and the upper yokes 16 and 17. Since the internal stress of any of the above films is considered to be isotropic, the stress applied to the MR element 13 in a film that is uniformly deposited on the MR element 13 like the gap insulating film 14 is Is considered isotropic. Therefore, it is considered that the stress-induced magnetic anisotropy based on the internal stress of the gap insulating film 14 does not occur in the MR element 13. However, the upper yoke 16
Anisotropy stress is applied to the MR element 13 from the film that is patterned and deposited in the vicinity of the MR element 13 like the 17th film, because these films are not arranged uniformly with respect to the MR element 13. .
Therefore, in the MR element 13, as shown in FIG. 7, magnetic anisotropy induced by stress is generated by the anisotropic stress. As shown in the figure, when the internal stress of the upper yokes 16 and 17 is the compressive stress δ _Y , a tensile stress δ _{MR in the} track width direction and a compressive stress δ ′ _{MR in the} width direction are generated in the MR element 13. In the following description, tensile stress is shown as> 0 and compressive stress is shown as stress <0.

Here, when the magnetostriction constant λ _s of the MR element 13 is negative, the stress-induced magnetic anisotropy is as shown in FIG. 8 in the track width direction, that is, the anisotropy of the MR element 13 during film formation. L perpendicular to the direction of
It occurs in the −L ′ direction. Therefore, in the MR element 13, the anisotropy direction becomes biaxial, and the direction of the magnetic anisotropy of the MR element 13 during film formation is disturbed, so that the anisotropy dispersion increases and the bulk・ Hausen noise is generated.
In FIG. 8, the direction of anisotropy on the MR element 13 is shown, and KK 'shows the direction of the induced magnetic anisotropy given at the time of film deposition of the MR element 13, and L-L ′ Is upper yoke 16 ・ 17
Indicates the direction of the stress-induced magnetic anisotropy induced in the MR element 13 by MM ', and MM' is the magnetic anisotropy in the MR element 13 as a result of combining the above two magnetic anisotropies. It shows the direction of sex. Since the direction of MM 'is inclined with respect to the longitudinal direction of the MR element 13, it is easy to cause a discontinuous change in magnetization.

On the other hand, it is practically difficult to form the upper yokes 16 and 17 in which the internal stress is zero so that stress-induced anisotropy does not occur. That is, as the yoke material, an Fe-Al-Si alloy, a Ni-Fe alloy, or the like is used, but the upper yoke 16/17 film is formed by any one of film forming methods such as sputtering, vapor deposition, and plating. However, internal stress peculiar to the upper yokes 16 and 17 film is generated. Therefore, it is impossible to reduce the internal stress while sufficiently maintaining the magnetic characteristics required for the yoke material. Therefore, the conventional structure has a problem that Barkhausen noise, which has a harmful effect on the head characteristics, cannot be eliminated.

[Means for solving problems]

In order to solve the above-mentioned problems, a magnetoresistive effect thin film head according to the present invention has a first yoke, a magnetoresistive effect element, and a second yoke each made of a ferromagnetic thin film on a substrate. In the magnetoresistive thin film head magnetically coupled in this order, when the internal stress of the first and second yokes is> 0, the magnetostriction constant of the magnetoresistive element is changed to the magnetostriction constant. When the internal stress is set to <0 while the internal stress is set to <0, the magnetostriction constant is set to a magnetostriction constant> 0.

[Work]

With the above configuration, the direction of the magnetic anisotropy of the magnetoresistive effect element, which is stress-induced by the internal stress generated in the first and second yokes, is changed to the original induced magnetic anisotropy of the magnetoresistive effect element. This is to prevent the occurrence of anisotropic dispersion by making it coincide with the direction of sex, and thus it is possible to suppress the generation of Barkhausen noise.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

In the magnetoresistive thin film head, as shown in FIG. 1, a sliding surface with the magnetic recording medium 2 is formed on one end surface 1a of a magnetic head substrate 1. The substrate 1 constitutes a lower yoke, and is a polycrystalline Ni-Zn ferrite substrate, a ferrite substrate such as a single-crystal or polycrystalline Mn-Zn ferrite substrate, or a non-magnetic substrate on which Ni-Fe, Fe-Al- is formed. It consists of a high-permeability substrate in which high-permeability thin films such as Si or Co-Zr are laminated. The track width of the magnetic recording medium 2 is often set to about 50 μm because the YMR head usually has a multi-track configuration. An insulating layer 3 is formed on the substrate 1 near the end face 1a, and a magnetoresistive effect element (hereinafter referred to as MR element) 4 is disposed on the upper surface of the insulating layer 3. The insulating layer 3 is made of SiO ₂ or the like. MR element 4 is Ni-Fe
Alternatively, it is made of a ferromagnetic thin film of Permalloy such as Ni-Co, and the film thickness is set to 200Å to 1000Å and the length is set to be substantially the same as the track width of the magnetic recording medium 2. Also MR
The magnetostriction constant of the element 4 is set so as to correspond to the positive and negative directions of the internal stress generated in the upper yokes 6 and 7 described later,
When the internal stress δ _Y of the upper yokes 6 and 7 is δ _Y > 0, the magnetostriction constant λ _S of the magnetoresistive effect element is set to λ _S <0, while the internal stress δ _Y is δ _Y < When it becomes 0, the magnetostriction constant λ _S is set to λ _S > 0.
Furthermore, when manufacturing the MR element 13, the easy axis of magnetization of the MR element 13 is selected in the track width direction. The MR element 13 converts the signal magnetic field generated from the magnetic recording medium 15 into a voltage change across the MR element 13 when a sense current I _S flows in the track width direction of the MR element 13. Further, on the substrate 1, the insulating layer 3 and the MR element 4, a gap insulating film 5 is formed so as to cover them. The insulating film 5 for the gap is made of SiO ₂ or the like. Furthermore, on the gap insulating film 5, each is made of a ferromagnetic thin film,
An upper yoke 6 that is a first yoke and a second yoke that is a second yoke forming a magnetic path of a magnetic recording signal detected from the magnetic recording medium 2 and an upper yoke 7 that are second yokes are provided in an opposing arrangement with a gap therebetween. . The upper yokes 16 and 17 are usually 0.5 to 4.0μ
It is made of a permalloy film having a thickness of about m. Then, the upper yoke 6, the MR element 4, and the upper yoke 7
Are magnetically coupled in this order.

Further, in the YMR head, a current I _B for generating a bias magnetic field is passed through a bias conductor (not shown) to apply a required bias magnetic field to the MR element 13 and move the operating point of the MR element 13 to a point having good linearity. Is configured.

In the above configuration, the MR element 4 has the predetermined magnetostriction constant λ _S set as described above. The magnetostriction constant λ _S of the MR element 4 can be set according to the manufacturing conditions of the MR element 4 film. However, for example, MR composed of Ni-Fe film
In the element 4, and the boundary conditions of the composition ratio of Ni is 79 to 82 [wt%], but positive and negative magnetostriction constant lambda _S reversed, the magnetostriction constant under the influence of the crystal orientation of the Ni-Fe film lambda _S order to make the transition, it is difficult to produce a Ni-Fe film as the zero magnetostriction constant _{λ S (J.Appl.Phys.52 (3),} March 1981 p2474
~ P2476 "The saturation magneto-striction of perm
However, it is easy to manufacture the MR element 4 by controlling the magnetostriction constant of the Ni—Fe film to be positive or negative of λ _S.

Therefore, the sign of the magnetostriction constant λ _S of the film of the MR element 4 is selected depending on whether the direction of the internal stress δ _Y of the film of the upper yokes 6 and 7 is positive or negative. An inverse magnetostrictive effect is given to the film of the MR element 4, and the influence can be reduced. Here, tensile stress in the case of [delta] _Y> 0, whereas, in the case of [delta] _{Y <0} is compressive stress, and has occurred in the membrane of the upper yoke 6, 7. That is, the upper yoke 6
When the direction of the internal stress δ _Y of the film of 7 is negative, the external stresses δ _MR and δ ′ _MR applied to the MR element 4 as a reaction of δ _Y are
As shown in FIG. 2, tensile stress acts in the longitudinal direction and compressive stress acts in the width direction. Here, δ _MR indicates the stress in the longitudinal direction of the MR element 4, and δ ′ _MR indicates the stress in the width direction of the MR element 4. When the direction of the internal stress δ _Y of the upper yoke 6 and 7 film is positive, the external stresses δ _MR and δ ′ _MR applied to the MR element 4 as a reaction of δ _Y are, as shown in FIG. Compressive stress and tensile stress work in the width direction. Therefore, the internal stress δ _{Y of} the upper yoke 6 and 7 film and the magnetostriction constant λ of the MR element 4 are
_By setting the relationship with _{S such} that δ _Y <0, λ _S > 0 δ _Y > 0, λ _S <0. The magnetic anisotropy L-L 'is in the longitudinal direction of the MR element 4. Since this magnetic anisotropy L-L 'coincides with the original direction of the induced magnetic anisotropy K-K', the direction of the synthesized magnetic anisotropy M-M 'is also in the longitudinal direction of the MR element 4. Match. Therefore, it becomes difficult for the discontinuous change in the magnetization in the MR element 4 to occur, and the internal stress of the upper yoke 6 and 7 films is
The characteristics of the MR element 4 are not adversely affected by Barkhausen noise and the like.

As a specific example, when a Ni-Fe sputtered film or a Co-Cr sputtered film is used for the upper yokes 6 and 7, the stress of the upper yokes 6 and 7 is generally a compressive stress.
The magnetostriction constant λ _S of the element 4 is set to be positive. When a Ni-Fe vapor deposition film or a Ni-Fe plating film is used for the upper yokes 6 and 7, the stress of the upper yokes 6 and 7 becomes tensile stress, so that the magnetostriction constant λ of the MR element 4 is Set _S to negative. Similarly, when using other yoke member, the magnetostriction constant of the MR element 4 in response to stress generated in the yoke material lambda _S
Select the positive or negative of.

〔The invention's effect〕

The magnetoresistive thin film head of the present invention, as described above,
A magnetoresistive effect thin-film head in which a first yoke, a magnetoresistive effect element, and a second yoke each made of a ferromagnetic thin film are magnetically coupled in this order on a substrate, And when the internal stress of the second yoke is greater than 0, the magnetostriction constant of the magnetoresistive effect element is set to be a magnetostriction constant <0, while when the internal stress is less than 0, the magnetostriction is The configuration is such that the constant is set to a magnetostriction constant> 0. As a result, the direction of the magnetic anisotropy of the magnetoresistive effect element, which is stress-induced by the internal stress generated in the first and second yokes, coincides with the original direction of the induced magnetic anisotropy of the magnetoresistive effect element. be able to. As a result, the occurrence of anisotropic dispersion in the magnetoresistive effect element is prevented, and Barkhausen noise is reduced. Therefore, it is possible to realize a magnetoresistive thin film head capable of faithfully reproducing a signal from the magnetic recording medium.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is a longitudinal sectional view showing a magnetoresistive thin film head, and FIGS. 2 and 3 are internal views of an upper yoke. Explanatory diagram showing the relationship between the stress, the stress generated in the magnetoresistive effect element with respect to the stress, and the magnetostriction constant of the magnetoresistive effect element, and FIG. 4 is an explanation showing the direction of the magnetic anisotropy of the magnetoresistive effect element. FIGS. 5 to 8 show a conventional example, FIG. 5 is a longitudinal sectional view showing a magnetoresistive effect thin film head, and FIG. 6 is a plan view showing a magnetoresistive effect thin film head.
FIG. 7 is an explanatory diagram showing the relationship between the internal stress of the upper yoke, the stress generated in the magnetoresistive effect element with respect to the stress, and the magnetostriction constant of the magnetoresistive effect element. FIG. 8 is the magnetic field of the magnetoresistive effect element. It is explanatory drawing which shows the direction of anisotropy. Reference numeral 1 is a substrate, 4 is a magnetoresistive effect element, 6 is an upper yoke (first yoke), and 7 is an upper yoke (second yoke).

Claims (1)

[Claims] 1. A magnetoresistive thin film head in which a first yoke, a magnetoresistive effect element, and a second yoke each made of a ferromagnetic thin film are magnetically coupled in this order on a substrate. When the internal stresses of the first and second yokes are such that internal stress> 0, the magnetostriction constant of the magnetoresistive effect element is set to magnetostriction constant <0, while when the internal stress <0, the magnetostriction constant is set to A magnetoresistive effect thin film head characterized by setting a magnetostriction constant> 0.