JPH0572644B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a magnetic head, and in particular to a magnetoresistive element (hereinafter MR This relates to a magnetoresistive head (hereinafter referred to as an MR head) that utilizes a magnetoresistive head (hereinafter referred to as an MR head).

(Prior art and its problems) As is well known, an MR element made of a ferromagnetic alloy thin film has high reproduction sensitivity to a signal magnetic field, and since it is a magnetic flux responsive type, the signal output does not depend on relative velocity and can be used even in the high frequency range. It has excellent features such as being able to obtain a constant output. Therefore, in the field of magnetic recording, it has been considered that MR elements with such excellent characteristics can be used as heads for high recording density reproduction, so-called MR heads, and various studies are being actively conducted.

Such an MR head usually has a structure in which an MR element is inserted between an upper and a lower magnetic shield made of a high-speed magnetic thin film through an insulating layer.
The magnetic shield blocks unnecessary leakage magnetic fields from magnetization transitions on the recording medium, suppresses saturation of the MR element and harmonic distortion, and efficiently blocks leakage magnetic fields from high-density recorded media. It has the effect of pulling up to the MR element well, and plays the role of improving the resolution of the MR head and the high frequency characteristics.

Therefore, it is essential that the material forming this magnetic shield has excellent soft magnetic properties. In particular, considering the trend toward higher recording densities in recent years, the characteristics required of magnetic shielding materials are increasing, and the conventionally used NiFe alloy (magnetic permeability μ = 1500, coercive force Hc = 0.5 Oe) change,
It is becoming extremely important for MR heads to construct magnetic shields using materials with even better properties and to fully demonstrate the effectiveness of the magnetic shields.

As one such magnetic shielding material, an amorphous soft magnetic material, for example, a Co-metal type amorphous soft magnetic material such as Co-Zr or Co-Zr-Nb can be considered.
These Co-metal amorphous materials, such as Co-
Zr film has a high magnetic permeability of 3500 even at 10MHz,
Furthermore, since it has a small coercive force of 0.03 Oe or less, it can provide a magnetic shield that is significantly superior to magnetic shields made of conventional NiFe alloys. However, this amorphous soft magnetic material has disadvantages in that it is thermally unstable, its magnetic properties change significantly over time, and its initially high magnetic permeability gradually decreases. Moreover, in principle, the MR element requires a sense current to flow through the MR element at all times;
The problem was that the magnetic shield that sandwiched the MR element was constantly exposed to heat generated by the sense current, which further accelerated the change in magnetic properties over time.

Such deterioration of magnetic properties naturally means a reduction in the effectiveness and function of the magnetic shield, and as a result, the head characteristics of the MR head also deteriorate.
This damaged the reliability of the MR head.

(Object of the invention) The object of the present invention is to eliminate these conventional drawbacks,
The object of the present invention is to provide a highly reliable MR head by controlling the deterioration of the characteristics of the magnetic shield.

(Structure of the Invention) The structure of the present invention is that a shield is formed by sandwiching an MR element made of a ferromagnetic thin film between two upper and lower magnetic shields made of a high magnetic permeability soft magnetic thin film, with an insulating layer interposed between them. In the MR head, at least one of the upper and lower magnetic shields is formed by laminating at least one layer each of an amorphous high magnetic permeability soft magnetic material and a crystalline high magnetic permeability soft magnetic material. It is characterized by being configured.

(Function of the Invention) By adopting the configuration of the present invention, the magnetic shield is constituted by a multilayer film in which at least two layers are laminated, one layer made of an amorphous soft magnetic material and the other layer made of a crystalline soft magnetic material. By magnetically coupling an amorphous soft magnetic thin film layer and a crystalline soft magnetic thin film layer, we suppress the deterioration of the magnetic properties of the magnetic shield, especially the decrease in magnetic permeability, and realize an excellent, highly reliable MR head. can do.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a partially sectional perspective view of an embodiment of the present invention. In this embodiment, the lower magnetic shield 12 is formed on a substrate 11 made of glass or ceramics using a thin film forming technique such as sputtering or vapor deposition and photolithography (sputtering was used here). Then, an MR element 14 made of a ferromagnetic thin film such as NiFe alloy is formed by vapor deposition via an insulating layer 13 made of a sputtered film, and a sense current is supplied to this MR element 14.
A terminal 16 made of a conductive material such as Au was formed using the same integrated thin film technology as the lower magnetic shield 12 (here, Au was formed by vapor deposition). After that, an insulating layer 13 (in this case, a SiO ₂ sputtered film) is formed again, and then an upper magnetic shield 15 is formed in the same way as the lower magnetic shield 12, and the shielded MR
The head is configured.

Here, both the upper and lower magnetic shields 15, 12 have a structure as shown in FIG. That is, a soft magnetic laminated film is formed by alternately stacking four crystalline soft magnetic layers 18 made of NiFe alloy with a thickness of 500 Å and three layers of CoZr amorphous soft magnetic layers 17 with a thickness of 3000 Å. , lower magnetic shields 15 and 12 are constructed.

When manufacturing this laminated film, the crystalline soft magnetic layer 18
In order to achieve magnetic coupling between the crystalline and amorphous soft magnetic layers 17, the films are formed in a magnetic field so that the easy magnetization axes of the crystalline and amorphous soft magnetic layers 18 and 17 are in the same direction. It is desirable to do so. This laminated film had excellent soft magnetic properties that are essential as a magnetic shielding material. In other words, it had soft magnetic properties far exceeding those of conventional magnetic shielding materials, such as NiFe alloys, with coercive force Hc = 0.03 to 0.05 Oe and magnetic permeability μ = 2500 to 3000.

Figure 3 shows the CoZr/NiFe laminated film shown in Figure 2, which serves as the magnetic shield for the MR head according to the present invention shown in Figure 1.
It is a graph showing the change in magnetic permeability over time when a CoZr single layer film (thickness: 10,000 Å) is left in the atmosphere at 80°C. In this figure, the solid line shows the change over time of the soft magnetic multilayer film according to the present invention having a film structure, and the broken line shows the change over time of the CoZr single layer film. Here, the horizontal axis shows the processing time, that is, the time left in the atmosphere at 80°C on a logarithmic scale, and the vertical axis shows the magnetic permeability μ ₀ before treatment, and the magnetic permeability μ(t) after t hours is normalized. It is shown. For measuring magnetic permeability, please refer to the magazine ``Review of Scientific Instruments''.
46 (1975), p. 904 of ``Instruments'', Vol. 46 (1975), page 904 was used. In other words, when a test sample is inserted into the lower part of a thin film coil formed in a figure 8 shape and the test sample is excited by another coil for applying a magnetic field, the magnetic flux determined from the amount of magnetic flux interlinking with the figure 8 coil. This was done by calculating the magnetic permeability from the ratio of the density and the excitation magnetic field. Moreover, the measurement frequency of this magnetic permeability is 5MHz.

As is clear from FIG. 3, according to the present invention
The decrease in magnetic permeability of the CoZr/NiFe laminated film is smaller than that of a single-layer film. For example, after 1000 hours,
The magnetic permeability of a single-layer film decreases to about 65% of its initial value, showing a large change over time, but in the multilayer film of the present invention, the decrease is only about 20%, indicating that the change in magnetic permeability over time is significant. has been improved.

That is, the rate of decrease in magnetic permeability D after 1000 hours is defined as the following equation.

D=μ ₀ − μ ₁₀₀₀ / μ ₀ ×100 (%) Here, μ ₀ and μ ₁₀₀₀ are the initial values of magnetic permeability, respectively,
Shows magnetic permeability after 1000 hours. In this case, a single layer film,
The reduction rates D ₁ and D ₂ of the laminated film are each expressed by the following equations.

D ₁ = 35 (%), D ₂ = 20 (%) The amount of decrease due to changes over time is reduced from 35% by the present invention.
improved to 20%.

As described above, the magnetic shield of the MR head according to the present invention has excellent soft magnetic properties, that is, high magnetic permeability and small coercive force, and there is little change in magnetic properties over time, suppressing the deterioration of the effectiveness and operation of the magnetic shield. Therefore, it has excellent characteristics and high reliability.

Furthermore, since the amorphous soft magnetic layer 17 and the crystalline soft magnetic layer 18 are magnetically coupled to each other, the magnetic domain structure of the magnetic shield is stabilized, and the interaction between the magnetic shield and the MR element is improved. Since the interaction is stable and reproducible, a highly reliable MR head can be obtained from this point as well.

Note that the configuration of the horizontal layer film in FIG. 2 is only an example.
The film thickness of each layer and the constituent material of each layer should be selected according to the specifications of each MR head. Furthermore, although this example shows an example in which the crystalline soft magnetic layer is first formed on the substrate, it is also possible to form the amorphous soft magnetic layer on the substrate first, or the crystalline soft magnetic layer may be formed on the substrate first. A configuration in which one layer and one amorphous soft magnetic layer are formed is also acceptable.

(Effects of the Invention) As described above, in the MR head of the present invention, the magnetic shield has excellent soft magnetic properties, and the change over time is significantly improved, and the magnetic domain structure of the magnetic shield is also stabilized. As a result, the interaction between the magnetic shield and the MR element is stable and reproducible, making it possible to realize a highly reliable MR head.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional perspective view showing the structure of an MR head according to an embodiment of the present invention, Fig. 2 is a cross-sectional view showing the structure of the upper and lower magnetic shields in Fig. 1, and Fig. 3 is the magnetic shield. It is a graph showing a change in magnetic permeability of a laminated film over time. In the figure, 11...substrate, 12...lower shield, 14...MR element, 15...upper shield, 1
7...Amorphous soft magnetic layer, 18...Crystalline soft magnetic layer.

Claims (1)

[Claims] 1. In a shielded magnetoresistive head formed by sandwiching a magnetoresistive element made of a ferromagnetic thin film between two upper and lower magnetic shields made of a high magnetic permeability soft magnetic thin film, each with an insulating layer interposed therebetween,
At least one of the upper and lower magnetic shields includes at least one layer each made of an amorphous high permeability soft magnetic material and at least one layer made of a crystalline high permeability soft magnetic material.
A magnetoresistive head characterized by being constructed by laminating layers.