JPS5911522A - Magnetoresistance effect head - Google Patents

Abstract

PURPOSE:To attain a magnetoresistance effect head having excellent reproducing characteristics, by providing rugged parts having plural pitches to a ferromagnetic thin film where its resistance is changed in response to a signal magnetic field. CONSTITUTION:A stripe pattern having different pitches is formed on a substrate 5 made of a ferromagnetic material such as Mn-Zn by using a photoresist, and the rugged parts of 0.02mu deep are formed by ion milling. The rugged parts are parallel in the direction of current and have different pitches in the direction of the width of the MR element, an anisotropic magnetic field Hk has a different value depending on the position in the broadwise direction and better biasing is executed by changing minutely the value of the Hk. It is possible to set uniformly the entire element to an excellent bias point by controlling locally the anisotropy of the MR element, the distortion is decreased, the dynamic range is increased and Barkhausen noises are reduced.

Description

Detailed Description of the Invention The present invention relates to a magnetoresistive head that detects changes in a signal magnetic field through changes in the resistance of a ferromagnetic thin film, and has a structure capable of applying a uniform bias magnetic field to the entire ferromagnetic thin film. I will provide a.

Conventionally, a magnetic head utilizing the magnetoresistive effect of a ferromagnetic thin film has been used as shown in FIG. That is, a magnetoresistive element (hereinafter abbreviated as MR element) 1 made of a ferromagnetic thin film is placed perpendicularly in close proximity to a recording medium 2, and a constant current 1 is passed between electrodes 3.4 arranged at both ends. M.R.
A substrate supporting element 1 is not shown. ). Then, a change in resistance value due to a signal magnetic field from the 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 specific resistance when there is no signal magnetic field, assuming that the total angle between the magnetization direction of the ferromagnetic thin film and the current direction is θ. It is expressed as ρ=ρ0+Δpm, CO32θ. Therefore, the ratio of the specific resistance change Δρ to the maximum specific resistance change Δpmax, Δρ/Δρmax i, has the characteristics shown in Fig. 2 for the applied magnetic field H.
Since it has significant nonlinearity with respect to the magnetic field, it is necessary to set the operating point at point P in FIG. 2 by applying a bias magnetic field HB. Methods for generating a bias magnetic field include passing a current through a conductor adjacent to the MR element (conductor bias method) and using magnetic poles of a thin film of a permanent magnet (hard film bias method), as shown in Figure 3. In either method, it is difficult to uniformly magnetize the entire ferromagnetic film to the optimum point. Note that the curve C in the figure shows the bias magnetic field by the conductance bias method, and the curve H shows the bias magnetic field by the hard film bias method. This is due to the following reasons.

Since the magnetization direction θ of the ferromagnetic film is determined by be. In the MR element shown in Fig. 1, in order to operate in the magnetization rotation region and avoid the hysteresis phenomenon, it is made uniaxially anisotropic so that the Z direction becomes the axis of easy magnetization, by means such as evaporation in a magnetic field. Oriented.

However, since HB+HD differs depending on the location depending on the thin film shape and bias magnetic field generation means, the magnetization direction becomes location dependent as shown in Figure 3, and the entire film cannot be placed at the optimal bias point, resulting in increased distortion and reduced output. This will result in a decline.

The present invention eliminates the above-mentioned conventional drawbacks, and by forming unevenness on a ferromagnetic thin film and changing the unevenness depending on the location to control the anisotropic magnetic field of the thin film, the MR element can be improved when no signal is biased. The purpose is to provide a magnetoresistive head that aligns the magnetization direction in a certain direction and has good reproduction characteristics.
If -1-HD is made equal to HB at each location, the magnetization will be oriented in the same direction throughout the MR element.

As a method of controlling the anisotropic magnetic field, if a ferromagnetic thin film is formed on a substrate with an uneven surface (pitch P, depth D) as shown in Figure 4, it will become smooth as shown in Figure 6. Compared to the anisotropic magnetic field HKo of a Ni-Fe film deposited in a magnetic field on a rough substrate, a large HK (i7) can be formed in the direction of the grooves on a rough substrate. Any HK″If you change the depth:
It is possible to realize an MR element with a large amount of power.

The present invention will be described in more detail below based on examples. As shown in FIG. 6, stripe patterns with different pitches are formed on a substrate 5 made of a ferromagnetic material such as Mn-Zn using 7-photoresist, and unevenness with a depth of 0.02 μm is formed by ion milling. . A non-magnetic insulating film such as 5i02 (r-qo) with a thickness of 5 μm is formed thereon by a method such as sputtering, and a non-magnetic conductive film such as T1 (6 f 0.2 pm) is formed thereon.

Ferromagnetic film i0.05μm such as Ni-Fe, vacuum evaporation, sputtering, or electrodeposition (hereinafter collectively referred to as evaporation)
Formed by means such as. The MR element 1 is shaped by lift-off using a photoresist mask.

Even if it is directly formed by a method such as mask plating, unnecessary parts can be etched by a method such as chemical etching, sputter etching, or ion milling (hereinafter collectively referred to as photolithography) using a photoresist mask after a thin film is completely deposited on the entire surface. ) may be formed. Furthermore, Cu on top of that,
A nonmagnetic conductive film 3 made of Al, Au, etc. is formed by vapor deposition and photolithography. After this, S i
A non-magnetic insulating material 8 such as O2 is deposited to a thickness of 0.7 μm, and a ferromagnetic thin film 9i such as Ni-Fe is further deposited to a thickness of 0.4 μm to form 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.

As shown in FIG. 7, the unevenness formed on the substrate 51- is parallel to the current direction and has a different pitch in the MR element 11 direction, and the anisotropic magnetic field HK is in the width direction as shown in FIG. It has different values depending on the position. Therefore, when a current is applied to elements 1 and 6 of the head shown in FIG. 6 to reach the optimum bias point, HB and HK-1-HD will become as shown in FIG. 9, and the direction of magnetization will be as shown in FIG. 10. As shown in FIG. 3, the entire MR element is biased better than in the case shown in FIG. This example shows an example in which the HK is changed in three stages, but it goes without saying that if the HK value is changed more finely, the bias will be better.

It should be noted that FIGS. 8, 9, and 10 are only diagrams for explaining the present invention in detail, and in reality, there is not such a steep change.

Although this embodiment has been described with respect to the case in which the substrate is made uneven, the unevenness may be formed directly on the surface of the ferromagnetic thin film.

Further, although this embodiment has been described with respect to a conductor bias type MR element, it goes without saying that the present invention can also be applied to MR elements with other bias methods and shapes.

As described above, the present invention makes it possible to uniformly set the entire element to a favorable bias point by partially controlling the anisotropy of the MR element.
Distortion is reduced and dynamic range is increased compared to conventional heads. Barkhausen noise is reduced because the anisotropy is controlled by the trench unevenness.

[Brief explanation of drawings]

Figure 1 is a perspective view to explain a conventional magnetoresistive head, Figures 2 and 3 are diagrams to explain its characteristics, and Figures 4 and 5 are diagrams for controlling the anisotropic magnetic field. For explaining the method, FIGS. 9 and 10 are diagrams for explaining the effects of this embodiment, respectively. 5...Substrate, 6...Nonmagnetic conductive film, 7
...Nonmagnetic insulating film, 8...Nonmagnetic insulating material, 9...Ferromagnetic thin film O Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure B h Figure 3 Q σ, 5 /θ ′/W Figure 4 Figure 5 Irregularity source zD(A) Figure 6, </ Figure 7 Figure 8 ρ Taro Iθ Y/w

Claims (1)

[Claims] A magnetoresistive head characterized by a ferromagnetic thin film whose resistance changes in response to a signal magnetic field, and at least one surface of which has concavities and convexities with a plurality of pitches.