JPS5963019A - Magneto-resistance effect head - Google Patents

Abstract

PURPOSE:To control an anisotropic magnetic field and to make magnetization approach in the same direction as a whole in an MR element by providing uneven parts on a ferromagnetic thin film, and also making depth of these uneven parts different from each other. CONSTITUTION:As for a method for forming uneven parts whose depth is different from each other, on a substrate consisting of a ferromagnetic material such as Mn-Zn, etc., a stripe-like mask 6 of a photoresist is formed on a substrate 5, and the exposed part is etched by a method (etching) such as chemical etching, spatter-etching, ion milling, etc. Subsequently, a part is covered with a photoresist mask 7 and is etched again, and thereafter, when the resist is peeled off, the substrate 5 having uneven parts of optional depth is obtained. Also, when a stripe-like pattern of SiO2 for instance, is formed on the whole surface by a lift- off method by use of the photoresist mask, and thereafter, a part of the mask is covered with the resist and also SiO2 is laminated on the remaining part, the substrate 5 which is formed by a stripe-like SiO2 layer 8 and has uneven parts whose depth is different from each other is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetoresistive head that detects changes in a signal magnetic field by changes in the resistance of a ferromagnetic thin film.

Conventional Structure and Problems Conventionally, RAD has been used for magnetism utilizing the magnetoresistive effect of a ferromagnetic thin film as shown in FIG. That is, a magnetoresistive element (hereinafter referred to as MR element) 1 made of a ferromagnetic thin film is arranged perpendicularly close to a magnetic recording medium 2, and a constant current i is passed between electrodes 3 and 4 arranged at both ends thereof. The change in resistance value caused by the signal magnetic field from the magnetic recording medium 2 is detected as a change in voltage between the electrodes 3 and 4.

The specific resistance ρ of the MR element 1 is the magnetization value of the ferromagnetic thin film. The angle between the current direction and the current direction is θ, and the specific resistance when there is no signal is ρ.

as ρ−ρ. +Δρmax cos2θ. Therefore, the ratio Δρ/Δρmax between the resistivity change Δρ and the maximum resistivity change Δρmax exhibits significant nonlinearity with respect to the applied magnetic field H as shown in FIG. It is necessary to set it at point P in Figure 2. Methods for generating a bias magnetic field include passing a current through a conductor adjacent to the MR element (conductance bias method: (C)) and using magnetic charges on a thin film of a permanent magnet (hard film bias method:
However, as shown in FIG. 3, it is difficult to uniformly bias the entire ferromagnetic thin film to the optimum point using either method.

This is due to the following reasons. The direction of magnetization θ of the ferromagnetic film is determined by H8: bias magnetic field, HS: signal magnetic field, HK: anisotropic magnetic field, and H9 two demagnetizing fields, so the direction of magnetization in the absence of a signal magnetic field is the optimum bias direction, for example 45°. In order to do this, it is necessary to make H2N (HK+KD). However, although H3 can be formed uniformly by deposition in a magnetic field, HB and H9 differ depending on the location depending on the element shape and bias magnetic field generating means, resulting in location dependence of the magnetization direction as shown in FIG. Here, C
is the case of the conductance bias method, and H is the case of the hard film bias method. Therefore, since the entire film cannot be placed at the optimum bias point, distortion increases and output decreases.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned conventional drawbacks and to provide a magnetoresistive head that has good reproduction characteristics by aligning the magnetization direction of the MR element in a constant direction during no-signal bias. It is.

Structure of the invention The invention is to provide unevenness to a ferromagnetic thin film and to vary the depth of the unevenness to create an anisotropic magnetic field HK.
This makes it possible to control the magnetization in the same direction throughout the MR element.

As a method of controlling an anisotropic magnetic field, a method is known in which a ferromagnetic thin film is formed on a substrate having an uneven surface (an uneven pitch P, the depth D) as shown in FIG. According to this formation method, a larger anisotropic magnetic field can be applied in the direction of the groove than when a film is formed on a smooth substrate in a magnetic field. For example, in the case of a Ni--Fe film, the anisotropic magnetic field HK on an uneven substrate changes significantly as shown in FIG. 5, compared to the anisotropic magnetic field HKo of a film deposited in a magnetic field on a smooth substrate.

Therefore, if you change the depth of the unevenness depending on the location of the board, HK
can be controlled.

DESCRIPTION OF EMBODIMENTS Hereinafter, the head of the present invention will be described in detail based on embodiments.

Irregularities with different depths are formed on a substrate made of a ferromagnetic material such as Mn-Zn. This method is shown in Figure 6 (A).
As shown in FIG. 2, a striped mask 6 of photoresist 1- is formed on a substrate 5, and exposed portions are etched by a method such as chemical etching, milling, or ion milling (hereinafter collectively referred to as etching). And the same figure (B
), cover a part with a photoresist mask 7,
After further etching, the resist is peeled off to obtain a substrate 5 having irregularities of arbitrary depth as shown in FIG. Furthermore, if a striped pattern of SiO2 is formed on the entire surface using a lift-off method using a photoresist mask, a part of the mask is covered with resist, and SiO2 is further laminated on the remaining part, as shown in FIG. In this way, a substrate 6 having irregularities of different depths formed by a striped 5i02 layer 8 is produced.

Next, a method of loading a head using the above substrate will be described.

As shown in FIG. 8, after forming unevenness with different depths on the surface of the substrate 5, a 5i film is formed on the uneven surface side by sputtering or the like.
A non-magnetic insulating film 9 such as 02 is formed to a thickness of 0.5-so μm, a non-magnetic conductive film 10 such as T1 is formed to a thickness of 2 μm, and a ferromagnetic film 11 such as N1-FC is formed to a thickness of 0.5 μm.
．． It is formed to a thickness of 0.5 μm by vacuum deposition, sputtering, electrodeposition, or the like (hereinafter collectively referred to as vapor deposition). Even if the MR element is directly formed by a method such as lift-off using a photoresist mask or mask plating,
It may also be formed by depositing a thin film over the entire surface of the substrate and then etching it using a photoresist mask. Furthermore, a nonmagnetic conductive film 12 made of Cu, Al, or Au is formed thereon by vapor deposition and photoetching. Thereafter, a nonmagnetic insulating film 13 such as ST02 is deposited to a thickness of 0.7 μm, and a ferromagnetic thin film 14 such as Ni-Fe is further deposited to serve as a shield. Next, a non-magnetic material such as SiO is deposited, and a protective cover such as glass is adhered (not shown) to form a head.

The unevenness formed on the substrate 5 is parallel to the current direction as shown in FIG. 9(A), and has a different depth in the width direction of the MR element as shown in FIG. 9(B). As shown in FIG. 10, has different values depending on the position in the width direction (W direction in FIG. 9(A)). That is, the greater the depth of the unevenness, the greater the HKO value. Therefore, when a current is applied to the thin film 10° 11 of the head shown in FIG.
The values of HD are as shown in Figure 11, and the values of H
The direction of magnetization determined by B/(HK+HD) is as shown in FIG. As is clear from these, it can be seen that the bias is better applied over the entire MR element than in the case shown in FIG.

Fig. 9 shows an example in which the HKO value is changed in three stages, but it goes without saying that if the HKO value is set even more finely, the bias will be even better.

In this embodiment, a case has been described in which irregularities are formed on the substrate, but the irregularities may be formed directly on the surface of the ferromagnetic thin film.

Effects of the Invention As described above, in the magnetoresistive head of the present invention, at least one surface of the ferromagnetic thin film is provided with unevenness, and the depth of the unevenness is varied. The magnetization direction can be aligned in a certain direction, and good reproduction characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the basic structure of a conventional magnetoresistive head, and FIGS. 2 and 3 are diagrams showing its characteristics. FIG. 4 is a diagram illustrating a method of controlling the anisotropic magnetic field, and FIG. 5 is a diagram illustrating the effect of its dimensions. 6 and 7 are cross-sectional views for explaining the manufacturing method of the main components of a magnetoresistive head according to the present invention, and FIG. 8 is a cross-sectional view of a magnetoresistive head according to an embodiment of the present invention. , FIG. 9 is a diagram showing an example of how the unevenness is formed, FIG. 10 is a diagram showing the distribution state of the anisotropic magnetic field value due to this, and FIG.
FIG. 12 and FIG. 12 are diagrams showing the characteristics. 5...Substrate with unevenness on the surface, e, 13...
...Nonmagnetic insulating film, 1o...Nonmagnetic conductive film, 11...Ferromagnetic film, 12...Nonmagnetic conductive film, 14...・Ferromagnetic thin film. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Fig. 4 Fig. 2 Fig. 3 Fig. 5 Unevenness, D (Z) Fig. 6 Fig. 7 Fig. 10 Oth Fig. 11

Claims (2)

[Claims] (1) A magnetoresistive head characterized in that at least one surface of a ferromagnetic thin film is provided with unevenness having different depths. (2) The magnetoresistive head according to claim 1, wherein the unevenness is formed in parallel, and the unevenness at the central portion is deeper than the unevenness located on both sides thereof.