JPS599987A - Magnetoresistance effect element - Google Patents

Abstract

PURPOSE:To detect a magnetic field bearing in a broad dynamic range, by providing uneven part on the surface of a substrate of a magnetoresistance effect (MR) element, aligning anisotropy in the uneven direction, increasing the magnitude of an anisotropic magnetic field by the uneven part, and enlarging a linear region. CONSTITUTION:Steps 12 are formed on the surface of a square substrate 14, on which an MR film 11 is to be deposited, so that the steps form 45 degrees with a current (i) that is flowed to the MR film 11. Electrodes 13 are provided at both ends of the MR so that the current can be uniformly conducted in the film. When the film 11 is evaporated on the substrate, the axis of the MR film 11, which can be readily magnetized, is directed to the direction along the uneven parts of the surface. The magnitude of an anisotropic magnetic field HK can be controlled by the repeating pitch and depth of the unevenness of the surface. When a magnetic field H is applied at a right angle with respect to the uneven direction, the change is resistivity delta0 indicates a straight line and has the maximum value when the H is small, and the polarity of the magnetic field can be judged. When the H is applied in parallel, the change is small and the value of change becomes the minimum in this direction. The relative angle between the magnetic field and the element can be read by comparing both values.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetoresistive (MR) elements applied to magnetic sensors, magnetic heads, etc., in which the magnetic domain structure is controlled by magnetostatically induced magnetic anisotropy. In addition to realizing the bias method, M that applied a new bias method
The purpose is to provide an R element.

Conventionally, as a basic structure of a magnetic head that utilizes the magnetoresistive effect, a magnetoresistive head having a strip-like element as shown in FIG. 1 has been considered. In the example shown in FIG. 1, a magnetoresistive element 2 made of a ferromagnetic thin plate is brought into contact with or close to the magnetic recording medium 1 perpendicularly (in the y direction), and electrodes are placed at both ends of the magnetoresistive element 2 in the longitudinal direction (two directions). 3 and 4 are arranged, a constant current i is passed between the electrodes 3 and 4, and the change in resistance value in the x direction is detected from the voltage change between the electrodes 3 and 4 using the signal magnetic field in the trench direction of the magnetic recording medium 1. It is a method. In this method, the signal magnetic field strength from the magnetic recording medium 1 decreases exponentially. In particular, in the region where the recording wavelength on the magnetic recording medium 1 is large, the growth of the signal magnetic field becomes very large. For this reason, it is desirable that the width W of the magnetoresistive element 20 is made as narrow as possible in consideration of processing accuracy, wear resistance characteristics, and the like.

The specific resistance change Δρ of the magnetoresistive element is determined by assuming that the ferromagnetic thin plate is uniaxially anisotropic, and the angle between the direction of magnetization M8 and the current l is θ,
When a and b are constants, the relationship Δρ=a + b cos θ holds true. The rate of change in resistivity obtained by dividing the impression force old 1 paper field H and the resistivity change Δρ by its maximum value Δρmax (
Δρ/Δρmax) has significant nonlinearity that saturates at H=Hs, and in order to improve this nonlinearity, it has significant nonlinearity that saturates at bias magnetic field HB, In order to improve this nonlinearity, it is necessary to apply a bias magnetic field HB to set ha to an appropriate operating point. At this optimal operating point, HB-Hs/I2,
θ-45°.

In a magnetoresistive element, a ferromagnetic thin plate oriented along the -axis is generally used in order to increase the rate of change in resistance and avoid hysteresis characteristics. -As an example, considering the strip-shaped element shown in Figure 2, the orientation is in the longitudinal direction of the element (
solid line), the orientation is stable, or in order to set the optimum operating point θ-45°, the bias magnetic field should be about the demagnetizing field in the direction perpendicular to the longitudinal direction of the element, that is, HB
=4πM6·t/w is required. Here, t indicates the thickness of the element 2. This becomes a fairly large magnetic field, and the magnetization is oriented in the direction of the fish reef, for example, with a magnetization component in the lateral direction. In other words, if we consider the case where the element is oriented a distance θ from the longitudinal direction of the element, the magnetic charge generated in the width direction of the element causes a real demagnetizing field and the magnetization M
Since the direction 6 is bent in the longitudinal direction, there is a problem in that it is difficult to maintain θ at the initial value.

In the present invention, by forming irregularities on the surface of the substrate on which the MR film made of ferromagnetic material is to be deposited, MR film can be deposited.
The direction of the magnetic anisotropy of the element and the magnitude of the anisotropic magnetic field are controlled, and the current applied to the MR element and fi (U, with the direction of the magnetic layer orientation substantially set at 45°, relative to the external magnetic field signal) are controlled. The purpose of this invention is to provide an element with good linearity and a new element that detects the direction of an external magnetic field.

FIG. 3(-) is an east view of an embodiment of the MR element according to the present invention, FIG. 3(b) is a cross-sectional view taken along line x-X,
Figures (C) and (d) show the MR characteristics.

N< 3 Ill As shown in (a) and (b),
An uneven step 12 is formed on the surface of the substrate 14 to which the quadrilateral MR 11 is torn so as to form an angle of 46 degrees with the current i that should flow through the MR IIK 11. Electrodes 13 are provided at both ends of the MR element film to ensure that current flows uniformly through the MR element.

A linear uneven step 1 on the surface of the substrate 14, like a child chain.
When the MR film 11 is steamed, the magnetization axis of the MR film 11 is directed in the direction along the surface irregularities of the base IJy, 14. Furthermore, the thickness of the anisotropic magnetic field generator is also [
) It can be controlled by repeated pinching and depth of the surface irregularities of the 1st century substrate 14.

Figure 4 shows the anisotropic magnetic field Hko of the MR film when the substrate surface is flat, and the anisotropic magnetic field Hko when the substrate surface is uneven.
The ratio of k, the repetition pitch P of the surface unevenness, and the depth D of the unevenness
It shows the relationship between In order to obtain a sufficiently large Hk with a shallow depth of depressions and depressions, the repetition pitch of the depressions and depressions needs to be approximately 0.5 μm. In order to obtain sufficient Hk with a pitch of 2 μm or more, a deep unevenness depth of 400 Å or more is required, and the reliability of the MR film will deteriorate if the step is equal to the thickness of the MR film. Smaller is preferable.

The anisotropic MR film obtained in this way is shown in Figure 3 (c
), exhibiting the characteristics shown in (d). Figure 3 (c
) shows the characteristics when a magnetic field H (sinusoidal) in a direction perpendicular to the uneven direction is applied, and Fig. 3(d) shows
This is a case where a magnetic field H is applied in a direction parallel to the direction of the unevenness. When H is applied perpendicularly to the direction of the surface unevenness, the ratio of the resistivity change Δρ to the resistivity ρ is Δρ/ρ. varies linearly in the region of small magnetic field, Δρ/ρ. The change in indicates the maximum.

In addition, the linearity is good, and depending on the direction of the magnetic field, Δρ/
ρ. It is possible to distinguish the polarity of the magnetic field because it changes in opposite directions. In addition, if H is one row for the unevenness, Δρ/ρ. The change in is small, Δρ/′ρ. The value of shows the minimum value in this direction. By comparing FIGS. 3(C) and 3(d), it can be seen that Δρ/ρ changes in the direction of the magnetic field so that 3600 is a minus period. That is, the relative angle between the magnetic field and the element can be read by the elements shown in FIGS. 3(a) and 3(b).

FIG. 5 shows another embodiment according to the present invention. Figure 3(a)
This is different from the embodiment shown in (b) by dividing the MR element into thin wires to increase the resistance, providing two elements that form a full angle of 900, and providing a midpoint terminal between them. be. This allows the direction of the magnetic field to be detected more clearly.

FIG. 5(b) shows the resistance value change of the left and right elements with respect to the magnetic field. When a current is passed from the left element to the right element as shown in Figure 5(a), the angle between the current and the surface unevenness provided on the board is 90 degrees, so the output from the left element relative to the midpoint is different. As , increases, the output to the midpoint of the right element decreases, and the selectivity to angle becomes more pronounced, as shown in Figures 5, et al.

FIG. 6 shows another embodiment according to the present invention. In this embodiment, two MR elements are provided which form an angle of 90 degrees. The angle between this and the unevenness on the substrate surface is 45°. A midpoint terminal is provided between these elements, a constant current is passed through the left and right elements, and the voltage generated in the pixel elements is read. In the configuration shown in Figure 6 (-), the two MR elements have an angle of 90 degrees, and the substrate surface irregularities, which are the easy magnetization axes of the two elements, form an angle of 9Q degrees. , it is possible to read the direction of the magnetic field in a more finely divided manner than in the example shown in FIG. Figure 6 (b
) shows the situation. Because the directions of the easy magnetization axes of the right and left elements differ by 90 degrees, the direction in which the minimum output occurs is different between the right and left elements9, and the current directions differ by 90 degrees. As shown in Figure 6, the output detected by the right element and the left element shows zero every 90 degrees, ten maximum points are detected at a phase of 90 degrees, and at a phase of 180 degrees. Indicates the minimum point -1. Unfortunately, the absolute values of the outputs become equal at 45°, the midpoint of the 90° phase difference that indicates the zero point of each element, and compared to the example shown in Figure 5, it is possible to obtain a more detailed and highly accurate magnetic field direction. can be detected.

As described above, in the present invention, irregularities are provided on the substrate surface of the MR element, the anisotropy of the MR element is aligned in the irregular direction f, and the magnitude of the anisotropic magnetic field Hk is made sufficiently large by the surface irregularities. By increasing the area and increasing the dynamic range, it is possible to provide a new MR element capable of detecting the strength of a crying magnetic field.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a conventional magnetoresistive element, and FIG. 2 is an explanatory diagram of the direction of magnetization thereof. FIG. 3(,) shows a magnetoresistive element 5 according to an embodiment of the present invention.
Plan view of the tongue Figure (b) is a cross-sectional view taken along the line X-X. (d) In the same figure (C), → is its characteristic diagram, FIG. 4 is a diagram showing the relationship between the anisotropic magnetic field and surface unevenness, and FIG. 6 (-) is a plan view of another embodiment of the present invention. , FIG. 6(b) is a diagram showing the relationship between the magnetic field direction and the output, FIG. 6(a) is a plan view of still another embodiment of the present invention, and FIG. 6(b) is a diagram showing the relationship between the magnetic field direction and the output. FIG. 11... Film having magnetoresistive effect, 12...
... Uneven step, 13... Electrode, 14... Substrate. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 4 Figure 5 tα2

Claims (1)

[Scope of Claims] (1) The substrate is made of a ferromagnetic material deposited on the substrate, and has projections and depressions formed on at least one surface, and the projections and depressions are provided linearly in a fixed direction on the − surface. The device has a pair of elements having a magnetoresistive effect even at an angle of approximately 45 degrees with respect to the unevenness, and has an intermediate terminal between the paired elements, and the paired elements are oriented at an angle of 90 degrees to each other. They are arranged to form an angle, and unevenness is formed on at least one surface of the pair of elements, and the unevenness is provided in an anisotropic linear shape in a certain direction on the - surface, and A magnetoresistive element characterized in that an angle between one side of the pair of elements and the projections and depressions is approximately 46 degrees. (3) The magnetoresistive element according to claim 2, wherein the unevenness formed on the surface of each of the at least one pair of elements forms an angle of 90 degrees for each element.