JPH1125430A - Spin valve type magneto resistance effect head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate a deviation due to rotation of the magnetizing direction and to avoid an obstruction of a magnetization vector by rotating the direction of fixed magnetization of a fixed layer from the same direction as the direction of a magnetic field generated by a sense current in the fixed layer by an amt. of an angle of rotation of the direction of bias magnetization of a free layer due to influence of the magnetic field by the sense current and also influence of magnetostatic coupling of the fixed layer. SOLUTION: A spin valve film 10 of the magneto-resistance effect head film (the fixed layer) 12 backed with a magnetically hard antiferromagnetic film 11 in switched connection and a spacer layer 3 held between this film 12 and the free layer 2 consisting of a magnetically soft magnetic film. The sense current Is flows into the spacer layer 3, and average magnetization of the free layer 2 is oriented toward the rotated direction by an angle α clockwise. The direction of a fixed magnetization vector in the soft magnetic film 12 is rotated clockwise from the direction perpendicular to the sense current by an angle β in a similar manner, and at the time of detecting operation of this element, the direction of magnetizing the fixed layer and the direction of bias magnetization of the free layer are orthogonally crossed to enhance the characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic head, and more particularly to a thin film magnetic head using a spin valve type magnetoresistive element (GMR element).

[0002]

2. Description of the Related Art A spin-valve magnetic sensor is a sensor element which has recently been spotlighted as a conversion element for detecting a magnetic quantity by converting it into a magnitude of electric resistance. First, the principle will be described. As shown in FIG. 12, the structure is such that one non-magnetic conductive layer is interposed between two magnetic layers, as schematically shown in an exploded perspective view. A fixed layer 1 magnetized in a predetermined fixed direction Mp, a free layer 2 whose magnetization direction Mf changes according to an external magnetic field, and a spacer layer 3 sandwiched therebetween are superimposed on each other. This utilizes a phenomenon in which the magnitude of the electric resistance exhibited by the spacer layer 3 changes in accordance with the magnetization direction Mf of the free layer 2. The magnitude of the electric resistance of the spacer layer 3 depends on the sense current I.
By flowing s, detection is made by the voltage drop during that time. To explain more microscopically, the pinned layer 1 is made of a soft magnetic film 12 lined exchange-coupled with a magnetized hard antiferromagnetic film 11, Under the influence of the magnetism, the soft magnetic film 12 (which serves as a substantial pinned layer, and may be hereinafter referred to as a “pinned layer” for convenience) shows a fixed magnetization vector in the same direction. The difficulty of the magnetization of the pinned layer 12 is generally referred to as an exchange bias magnetic field Hua.
If the value of ua is large, the direction of magnetization of the pinned layer hardly changes due to an external magnetic field. The free layer 2 is a soft ferromagnetic film, and easily changes and magnetizes according to magnetic induction (magnetostatic coupling) from a nearby external magnetic field that affects the free layer.

The electric resistance value exhibited by a spin valve magnetic sensor changes depending on the angle between the magnetization direction of the pinned layer and the magnetization direction of the free layer, and is measured for an actual spin valve element. The result is shown in the graph. FIG. 13 is a graph showing the resistance R with respect to θ, where θ is the angle between the magnetization direction Mp of the pinned layer 1 and the magnetization direction Mf of the free layer 2.
This is a graph showing the change of. The actual measurement value of this example is as written in the memory of the graph, but the average resistance value is 93.43 [Ω], the variation width of the resistance value is 4.64 [Ω], and the variation width of the resistance value Ratio (GMR ratio)
Is 4.97%, which is measured at a sense current of 10.0 mA. As can be seen from this graph, the resistance value changes almost symmetrically around θ = 90 degrees. That is, the change in the direction of Mf is represented by R
Can be detected as a change in the value of. For example, if a portion having good linearity in the range of θ = 30 to 150 degrees is used, a converter (magnetoresistive element) of a magnetic amount to an electric resistance having good linearity can be manufactured. This type of magnetoresistive element has a GM
Commonly called an R element.

A schematic structure of a spin-valve magnetic head utilizing the above principle is illustrated in FIG. 14A shows a state in which the sense current Is is flowing through the spin valve film 10, and FIG.
0 is disassembled to show the detailed configuration. The spin valve film 10 is formed by stacking an antiferromagnetic film 11, a soft magnetic film 12, a spacer layer 3, and a free layer 2. The flow of electrons in the spacer layer 3 is affected by the degree of magnetization of the magnetic films on both sides sandwiching the spacer layer 3, and the spin valve film 1
0 indicates a resistance value for the sense current Is accordingly. The fixed layer 12 is hardly magnetized in the direction of the arrow Mp. The free layer 2 is used by being magnetized as its operating center in the direction of the arrow Mf. When the free layer 2 is exposed to an external magnetic field, and the direction of the Mf is changed before and after the set central angle in accordance with the magnitude of the external magnetic field, the resistance of the spin valve film 10 causes the magnetization of the operation center to change. It changes before and after the corresponding resistance value. Thus, the magnitude of the external magnetic field is detected as a resistance value. Where Mp and M
The direction of f is set orthogonally as the operation center as shown in the figure.

[0005]

Next, a situation where the spin valve film is actually operated as a detecting element will be described with reference to FIG. Spin valve film 10
Then, a sense current is caused to flow in the direction of arrow Is. This sense current mainly flows through the spacer layer 3 (which is a good conductor metal). At this time, the magnetic field due to the sense current (the magnetic field according to the right-hand screw rule of ampere) is the same as the original magnetization direction Mp at the pinned layer 12 located on the spacer layer 3, At the free layer 2 located below the layer 3, the orientation is opposite to the above Mp. Further, an induced magnetic field due to magnetostatic coupling from the fixed layer 12 is also induced in the free layer 2 in a direction opposite to the above Mp. Therefore, in the free layer 2, the sum of the magnetic field caused by the sense current Is and the magnetic field induced by the fixed layer 12 is added, and as a result, the angle α shown in FIG.
However, the direction of the operating center magnetic field of the free layer 2 rotates (shifts) in the direction rotated clockwise (= clockwise). FIG. 16 shows this state when viewed from directly above.

In order to compensate for the undesired rotation of the direction of the magnetization vector, the direction of the sense current is reversed to cancel out the magnetic field caused by the sense current Is and the magnetic field caused by the fixed layer magnetization in the free layer 2. However, in this case, the magnetic field due to the sense current Is in the pinned layer 12 tends to cancel the original Mp in this case, and the desired operation is jeopardized. In particular, the value of the exchange coupling bias Hua generally depends on temperature, for example, as shown in FIG. 17, and the magnetization of the pinned layer 12 becomes smaller as the temperature rises, and thus disappears or reverses under the influence of the sense current Is. Can happen. The temperature of the element may be 100 ° C. or more due to heat generated by the sense current, and when the element collides with a rotating magnetic disk or the like, the temperature of the element may rise rapidly due to frictional heat. Therefore, it is not preferable to induce a magnetic field in a direction that cancels the magnetization in the direction of Mp.

Therefore, the present invention compensates for the shift due to the rotation of the magnetization direction of the operating center of the free layer, and
An object of the present invention is to provide a spin-valve magnetoresistive head that does not hinder the original magnetization vector of the pinned layer.

[0008]

SUMMARY OF THE INVENTION According to the present invention, the rotational deviation of the magnetization direction of the problem is changed from the beginning by changing the direction of the magnetization of the pinned layer to the extent that the magnetization of the free layer will be deviated by rotation. By shifting the setting, compensation is attempted. In addition, the direction of the magnetization of the pinned layer with respect to the sense current is set to the same side as the direction of the magnetic field generated around the sense current, so that undesired disappearance of the pinned layer magnetization due to the influence of the sense current does not occur. doing.

That is, a spin-valve magnetoresistive head according to the present invention includes a spin-valve magnetoresistive element having a conductive spacer layer and a soft magnetic free layer and a hard magnetic pinned layer sandwiching the conductive spacer layer from both sides. The orientation of the pinned magnetization of the pinned layer is changed by an angle corresponding to the angle of rotation of the bias magnetization of the free layer due to the influence of the magnetic field due to the sense current and the effect of the magnetostatic coupling of the pinned layer. By rotating from the same direction as the direction of the magnetic field due to the sense current in the
The structure is such that the direction of magnetization of the pinned layer and the direction of bias magnetization of the free layer are orthogonal to each other during the detection operation of the element.

[0010]

The direction of magnetization of the pinned layer is substantially perpendicular to the direction of magnetization of the operating center of the free layer, so that the operating center may be located substantially at the center of the range of change in the resistance value of the spacer layer. As a result, the range of change in resistance can be widened, and the linearity of change can be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A spin valve type magnetoresistive head according to the present invention will be described below with reference to the drawings. In FIG. 1, part (a) shows a spin valve film 10, which is a main part of the spin valve magnetoresistive head of the present invention, to which a sense current Is is supplied. Part (b) illustrates the main components by disassembling the spin-valve film 10 in its thickness direction, and shows a pinned layer 12 lined with a magnetically hard antiferromagnetic film 11 by exchange coupling. And a free layer 2 made of a magnetically soft magnetic film. The sense current Is flows through the spacer layer 3. The normal magnetization of the free layer 2 is oriented clockwise (in the figure) by the angle α as shown in the figure. On the other hand, as shown in the figure, the direction of the fixed magnetization vector in the pinned layer 12 is shifted from the direction perpendicular to the sense current (and the direction perpendicular to the same direction as the magnetization by the sense current) by the angle β, as shown in FIG. It is set to rotate around. FIG. 2 illustrates this state when viewed from directly above. The value of the angle β will be described in detail with analysis and examination below.

Here, the direction of magnetization in the free layer 2 will be observed microscopically with reference to FIG. FIG. 3A is a front view of a spin valve element incorporated as a spin valve head, in which the horizontal direction is the element length direction and the vertical direction is the element height. Direction
The direction perpendicular to the plane of the drawing is the thickness direction of the element. As shown in the figure, the element portion which is the spin valve film 10 has a lead portion for supplying a sense current to both ends in a longitudinal direction thereof and a direction for magnetization (bias magnetic field) of an operation center of the free layer. A longitudinal bias magnet is coupled. The free layer of the element part is induced by magnetostatic induction from the longitudinal bias magnet.
Each part in the figure is magnetized in the direction shown by the small arrow. In other words, at both ends in the length direction of the element portion (corresponding to the track end portion at the time of reading), the direction of magnetization is aligned with the longitudinal direction due to the strong influence of the magnetic field of the longitudinal bias.
The direction of the magnetization rotates clockwise under the influence of the sense current Is in the middle of the element portion away from it, and the rotation angle (α described above) increases. This rotation angle α
FIG. 3B shows a distribution state of (magnetization direction) corresponding to a position in the element portion. That is,
α is 0 at both ends of the element portion, gradually increases toward the center, and reaches a maximum at the center.

Next, the direction of the pinned magnetization of the pinned layer will be analyzed. First, when there is no rotation angle β of the pinned magnetization direction, that is, when β = 0, the sensitivity at each position of the element unit is observed microscopically. Since α = 0 at both ends of the track, that is, both ends of the element portion, the magnetization directions of the free layer and the pinned layer are orthogonal to each other, and
There is no bias point shift. However, the rotation of the magnetization direction of the free layer becomes stronger toward the center of the element portion, and the angle α increases. For this reason, the sensitivity characteristics (microtrack profile) at each position in the element viewed microscopically are high at both ends of the track and low at the center of the track. In FIG. 4, part (a) depicts the distribution of the direction of the bias magnetization at each point in the free layer, and part (b) depicts the sensitivity of the element at each position. In this case, the output characteristic of the shift from track is as shown in FIG. 5, and the off-track profile has a shape in which the center portion (middle part of the slope) swells in a stepped manner.

Next, when the angle β of the direction of the pinned magnetization is equal to the angle α _max of the magnetization direction at the center of the free layer, that is, when β = α _max , the sensitivity at each position of the element portion is determined. Observe microscopically. At both ends of the track, that is, at both ends of the element portion, the direction of magnetization of the free layer is not orthogonal to the direction of magnetization of the fixed layer, and the bias points are shifted. However, as the position approaches the center of the device, the relationship between the direction of magnetization of the free layer and the direction of magnetization of the pinned layer approaches an orthogonal state, so that the sensitivity of the GMR effect increases and the microtrack profile characteristic of the spin-valve device increases. 6 is higher at the center of the track than at both ends of the track, as shown in FIG. However, in this case, the output characteristic of the deviation from the track is as shown in FIG. 7, and the off-track profile has a shape with a concave center (a concave curve below). In other words, the characteristics exhibit a sharp increase in sensitivity in the on-track state.

Further, a method for improving the linearity of the off-track profile by appropriately selecting the angle β of the direction of the pinned magnetization will be described. For this purpose, the direction of the pinned magnetization of the pinned layer is selected to be β = α _max / √2. By doing so, the output characteristics of the deviation from the track become as shown in FIG. 8, and the slope portion of the off-track profile can be substantially linearized.

The angle β of the direction of the pinned magnetization is
Is naturally selected between 0 and α _max , but 0 <β <α _max / √2 due to the above-mentioned constraint of maintaining the linearity of the off-track profile. Here, since α _max cannot be more than 90 degrees, from this viewpoint, the numerical value of the angle is in the range of 0 <β <64 degrees. From this range, when an experiment was performed on the value of β, when the sense current was 2 mA or more, β
Was β> 5 °. In addition, the upper limit of β was β <40 °, which is a limit at which the sensitivity of the entire spin valve element can secure 0.7 times or more of the maximum sensitivity value of the microscopic sensitivity distribution. When the angle is larger than this, the detection component due to the magnetization vector in the fixed direction is not added any more, and the signal sensitivity sharply decreases.

Therefore, in the present invention, the magnitude of the rotation angle β of the magnetization of the pinned layer is selected in the range of 5 to 40 degrees. Further, as the optimum angle, an angle at which the linearity of the off-track characteristic is best in this angle range is selected. As an experiment, free layer magnetization: Mf 1.4 [T] Free layer thickness: tf 2.5 [nm] Fixed layer magnetization: Mp 1.4 [T] Fixed layer thickness: tp 2.0 [nm] Track Width: 1.2 [μm] Element Height: 1.0 [μm] Spacer Thickness: 2.5 [nm] Sense Current: 5.0 [mA] For the element having the rotation angle β of the magnetization direction of the fixed layer and the rotation angle β. When the relationship with the sense output was examined, the result shown in FIG. 9 was obtained. From this graph, it can be seen that the maximum sensitivity is obtained in the range of 10 ° <β <30 ° as the rotation angle β. The variation in sensitivity at this rotation angle was at most -7% or less.

In this case, when the symmetry of the waveform was examined with respect to an external magnetic field of ± 3200 A / m, the relationship shown in FIG. 10 was obtained. Here, the horizontal axis represents the rotation angle β of the magnetization direction of the pinned layer, and the vertical axis represents the waveform symmetry as a percentage of the peak asymmetry PA. From this graph, it is understood that the symmetry of the waveform can be suppressed to within ± 5% when the rotation angle β is set in the range of + 5 ° to + 40 °.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, a specific configuration of a GMR head in which the pinned magnetization is devised according to the present invention will be described. FIG. 11 is a perspective view illustrating a main part of an actual model of a magnetoresistive head constituted by connecting each layer of the spin valve element film of the present invention to a longitudinal bias magnet and a lead for supplying a sense current, The near side is the side facing the magnetic recording medium, the left-right direction is the direction of the track width, and the up-down direction is the traveling direction of the track. In the figure, 1 is a fixed layer, 2 is a free layer, 3 is a spacer layer, 22 is a longitudinal bias magnet layer, and 23 is a lead layer. The sense current is supplied from the lead layer of the good conductor, flows across the bent portions of both ends of the free layer 2 in the thickness direction, and flows through the spacer layer of the good conductor in the length direction. The longitudinal bias magnet layer 22 gives a bias magnetization to the free layer 2. In FIG. 11, the portion of the spin valve film is schematically illustrated in three layers based on the operation principle. However, when the model as an actual example is described in more detail, the free layer 2 From CoZrNb amorphous magnetic layer 8 nm, NiFe layer 1.5 nm, CoFe layer 2.0 n
m are laminated. The three spacer layers are a Cu layer having a thickness of 2.0 nm. The fixed layer 1
It is preferable that a film having a thickness of 2.0 nm and a film of IrMn having a thickness of 8 nm are laminated from below.

Next, a method for imparting orthogonal magnetization to the pinned layer of the spin valve head having the structure of the present invention will be described.
First, in order to impart anisotropy to the free layer, a magnetic field of 240 kA / m is applied in the direction (longitudinal direction) of the bias magnetization of the free layer, while applying a magnetic field at 250 ° C. (blocking temperature of the antiferromagnetic film) in a vacuum. Heat treatment for more than an hour. Then, 200-2
After cooling to 30 ° C., the externally applied magnetic field is rotated to the above-mentioned 90 ° + β, which is the direction of the pinned magnetization of the fixed layer, that is, 90 ° + 5 to 40 °, and cooling is continued in that state. This cooling is performed at a rate of 100 ° C./hr or more. By the heat treatment described above, the device is provided with the anisotropy in the longitudinal direction of the free layer of the soft magnetic material and the orthogonal magnetization of the fixed layer obtained by adding the rotation of the angle β to the magnetization direction of the fixed layer of the hard magnetic material. Can be granted.

[0021]

As described above, according to the present invention, the direction of the pinned magnetization of the fixed layer is oriented in the direction to correct the angular deviation of the direction of the bias magnetization in the use state of the free layer. In operation, the optimal orthogonalization of both magnetization directions can be ensured, and an element having good waveform symmetry and sensitivity of the detection output with respect to the magnetic recording waveform can be realized.
Further, since there is no possibility that the magnetization direction of the fixed layer is counteracted by the magnetic field caused by the sense current in the opposite direction, it is possible to obtain a head capable of stably obtaining an output even when the use environment temperature rises.

[Brief description of the drawings]

FIG. 1 is a perspective view of a spin valve element which is a main element in a spin valve type magnetoresistive head according to the present invention.

FIG. 2 is a plan view illustrating the direction of magnetization of the spin valve element of FIG.

FIG. 3 is a plan view and a graph showing a magnetization direction distribution of a free layer of the spin valve element.

FIG. 4 is a diagram showing a sensitivity distribution corresponding to a magnetization direction distribution of a free layer of a spin valve element when a rotation angle β of a magnetization direction of a pinned layer is set to 0.

FIG. 5 is a graph showing the output characteristics of the spin valve element with respect to track deviation when the rotation angle β of the magnetization direction of the pinned layer is set to 0.

FIG. 6 is a diagram showing a sensitivity distribution corresponding to the magnetization direction distribution of the free layer of the spin valve element when the rotation angle β of the magnetization direction of the pinned layer is equal to the maximum rotation angle α of the bias magnetization direction of the free layer. is there.

FIG. 7 is a graph showing output characteristics of the spin valve element with respect to off-track when the rotation angle β of the magnetization direction of the pinned layer is equal to the maximum rotation angle α of the bias magnetization direction of the free layer.

FIG. 8 is a graph showing output characteristics of the spin valve element with respect to off-track when the rotation angle β of the magnetization direction of the pinned layer is set to 1 / √2 of the maximum rotation angle α of the bias magnetization direction of the free layer. .

FIG. 9 shows a spin valve element according to the present invention.
6 is a graph showing how the output changes during on-track with respect to a change in the rotation angle β of the magnetization direction of the pinned layer.

FIG. 10 is a graph showing how the symmetry of the detected waveform changes with respect to the change in the rotation angle β of the magnetization direction of the pinned layer in the spin valve element according to the present invention.

FIG. 11 is a perspective view showing a structure near a spin valve element of a spin valve magnetoresistive head according to the present invention.

FIG. 12 is an exploded perspective view illustrating the principle of a spin valve element.

FIG. 13 is a graph showing how the resistance of the spin valve element changes with respect to the change in the magnetization direction θ of the free layer with respect to the magnetization direction of the pinned layer of the element.

FIG. 14 is a perspective view of a conventional spin valve element.

FIG. 15 is a perspective view illustrating a rotation phenomenon of a magnetization direction of a free layer in a conventional spin valve element.

16 is a plan view illustrating the direction of magnetization of the spin valve element of FIG.

FIG. 17 is a graph showing how the exchange coupling magnetic field changes with the temperature of the material of the pinned layer used in the spin valve element.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 fixed layer, 2 free layer, 3 spacer layer, 10 spin valve film, 11 antiferromagnetic film, 12 soft magnetic film, 2
2: Longitudinal bias magnet layer, 23: Lead layer, Mp: magnetization direction of fixed layer, Mf: magnetization direction of free layer, Is: sense current, α: rotation angle of magnetization of free layer, β: rotation angle of fixed layer Rotation angle of magnetization.

Claims (3)

[Claims] In a spin-valve magnetoresistive element having a conductive spacer layer, a soft magnetic free layer sandwiching the conductive spacer layer from both sides, and a hard magnetic pinned layer, the direction of bias magnetization of the free layer is a magnetic field caused by a sense current. By rotating the direction of the pinned magnetization of the pinned layer from the same direction as the direction of the magnetic field due to the sense current in the pinned layer by the amount of angle corresponding to the angle of rotation caused by the effect of Wherein the direction of magnetization of the pinned layer and the direction of bias magnetization of the free layer during operation of detecting the element are substantially orthogonal to each other. head. 2. The magnetoresistive head according to claim 1, wherein the angle for rotating the direction of the pinned magnetization of the pinned layer is 5 to 4.
A head selected in the range of 0 degrees. 3. The magnetoresistive head according to claim 2, wherein the angle for rotating the direction of the pinned magnetization of the pinned layer is 10 to 10.
A head selected in a range of 30 degrees.