JP3048552B2 - Magnetic recording / reproducing method and magnetic recording / reproducing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing method and a magnetic recording / reproducing apparatus using a reproducing magnetic head having high sensitivity.

[0002]

2. Description of the Related Art With the increase in density of magnetic recording, a magnetoresistive head having a giant magnetoresistance effect has begun to be used as a reproducing magnetic head. Materials showing a giant magnetoresistance effect include Physical Review B by Diany et al.
Vol. 3, No. 1, pp. 1297-1300.
Magneto-resistance in Soft Ferromagnetic Multilaye
As in "rs", a multilayer film in which two magnetic layers are separated by a nonmagnetic layer and an exchange bias magnetic field from an antiferromagnetic layer is applied to one magnetic layer has been devised. Jason by Hoshino et al.
panese Journal of Applied Physics, Vol. 34, No. 3
No., pp. 1526-1533, "Magnetoresistanc"
The giant magnetoresistance effect has been observed even in a multilayer film in which two magnetic layers having different coercive forces are separated by a nonmagnetic layer, such as "E Effects in Ni-Fe-Co / Cu / Co-Pt Trilayers". .

[0003]

In a multilayer film in which two magnetic layers having different coercive forces are separated by a non-magnetic layer, conventionally,
It has been required that one magnetic layer (magnetic layer A) has a high coercive force and the other magnetic layer (magnetic layer B) has a low coercive force. However, as described in the above-mentioned report by Hoshino et al., The leakage magnetic field from the magnetic layer A having a high coercive force is applied to the magnetic layer B having a relatively low coercive force, so that the magnetic layer B has a high coercive force. There was a problem that would be.
When the coercive force of the magnetic layer A is reduced, the application of the leakage magnetic field as described above is eliminated, so that the coercive force of the magnetic layer B does not increase. However, in a conventional magnetic recording / reproducing apparatus that performs reproduction by utilizing a gradient of a voltage change between electrodes of a magnetoresistive head, if the coercive force values of the magnetic layers A and B are close, the linearity of the voltage change is reduced. The reproduction is problematic due to the small area.

The present invention has been made in view of such a problem, and provides means for performing high-performance magnetic recording and reproduction using a magnetic head having two types of magnetic layers having a small difference in coercive force. The purpose is to:

[0005]

The present inventors have conducted intensive studies on a method of reproducing magnetic recording by a magnetoresistive head using a multilayer film having two types of magnetic layers having different coercive forces. Instead of detecting the gradient of the voltage change between the two layers, the magnetizations of both magnetic layers are reversed at different timings by the magnetic field applied from the magnetic recording medium, and the angles formed by the magnetizations of the two magnetic layers become antiparallel. The present inventors have found that magnetic recording can be reproduced by detecting an increase in magnetic resistance (voltage peak) due to this, and have completed the present invention.

The magnetoresistive head used in the method of the present invention is a magnetoresistive head having a multilayer film in which a first magnetic layer and a second magnetic layer are laminated with a nonmagnetic layer interposed therebetween.
Ri, the first magnetic layer has a coercive force of the magnetization by the magnetic field applied from the magnetic recording medium is reversible size, the second magnetic layer is smaller coercive force than coercive force of the first magnetic layer Can be included .

The direction of easy magnetization of the first magnetic layer is substantially parallel to the direction of the magnetic field applied from the magnetic recording medium, and the direction of easy magnetization of the second magnetic layer is the direction of the magnetic field applied from the magnetic recording medium. It is preferable that they are almost orthogonal to each other in terms of detecting a magnetic field from a magnetic recording medium at a high frequency.
Further, the magnetoresistive head used in the method of the present invention is:
A magnetoresistive head comprising a first magnetic layer and the multilayer film and a second magnetic layer laminated sandwiching the nonmagnetic layer, the first
The easy direction of magnetization of the magnetic layer is substantially parallel to the direction of the magnetic field applied from the magnetic recording medium, and the easy direction of magnetization of the second magnetic layer is substantially orthogonal to the direction of the magnetic field applied from the magnetic recording medium. The first magnetic layer has a coercive force whose magnetization can be reversed by a magnetic field applied from a magnetic recording medium, and the second magnetic layer has an anisotropic smaller than the coercive force of the first magnetic layer. it can be assumed to have a sex field.

[0008] The magnetic recording / reproducing method according to the present invention is different.
A magnetic field having a coercive force and applied together from the magnetic recording medium
The first magnetic layer whose magnetization is reversible depending on the direction of
And a magnetic layer applied to the multilayer film from a magnetic recording medium .
Therefore, the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are both
And detecting a change in magnetoresistance of the multilayer film due to a temporary antiparallel angle between the magnetization of the first magnetic layer and the magnetization of the second magnetic layer.

According to this magnetic recording / reproducing method, the fact that the magnetic resistance of the multilayer film has exceeded a predetermined value is detected by the voltage between the electrodes through which a constant current flows through the multilayer film. Reversal of the recorded magnetization can be detected. A magnetic recording / reproducing apparatus according to the present invention includes a magnetic recording medium, a recording medium driving unit for driving the magnetic recording medium, a magnetic head including a signal recording unit and a signal reproducing unit, and a magnetic head driving unit for driving the magnetic head. A magnetic recording / reproducing apparatus including a magnetic head recording / reproducing signal processing means,
The magnetic head includes, as the reproducing section, a magnetoresistive head having a multilayer film in which the above-described two magnetic layers are stacked with a nonmagnetic layer interposed therebetween, and the recording / reproducing signal processing means detects a detection signal from the magnetoresistive head. Is characterized in that the sign of the signal recorded on the magnetic recording medium is inverted when the value exceeds a predetermined value.

In a magnetic recording / reproducing apparatus having a magnetoresistive head using a multilayer film formed in the order of a first magnetic layer, a nonmagnetic layer and a second magnetic layer, the first magnetic layer and the second magnetic layer When the coercive forces of the two magnetic layers are different, the magnetic field applied from the magnetic recording medium to the multilayer film of the head changes the angle between the magnetizations of the two magnetic layers to parallel, anti-parallel, and parallel. At this time, a peak occurs in the voltage between the electrodes of the magnetoresistive head due to the cycle of the change of the angle of magnetization between parallel, anti-parallel, and parallel. Since this voltage peak indicates that the polarity of the magnetic field applied from the magnetic recording medium has changed, magnetic recording can be reproduced by detecting the voltage peak.

By using this method, two types of magnetic layers having a small difference in coercive force can be used. That is, the coercive force of the magnetic layer having the higher coercive force can be made relatively low. Since a magnetic layer having a relatively low coercive force can be used, a high-sensitivity magnetoresistive head can be configured without impairing the soft magnetic characteristics of the magnetic layer.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows two different coercive forces.
FIG. 1 is a schematic cross-sectional view showing a structure of a multilayer film 10 according to the present invention in which magnetic layers are separated by a non-magnetic layer and stacked. In FIG. 1, the substrate 11 is a single crystal of Si (100), the magnetic layer 12 is a Co layer having a thickness of 5 nm, and the non-magnetic layer 13 is 2.5 n thick.
5 nm thick Ni-20a on the Cu layer and the magnetic layer 14.
A t% Fe alloy layer was used. The coercive force of the magnetic layer 12 is 800
A / m, the coercive force of the magnetic layer 14 is 80 A / m, and the anisotropic magnetic field is 400 A / m. The multilayer film 10 was patterned, and electrodes were formed at both ends of the multilayer film to produce a magnetoresistive element.

When the magnetoresistive element having the multilayer film 10 is used as a reproducing head of a magnetic head, the magnetic field intensity applied from the magnetic recording medium to the multilayer film 10 controls the distance between the magnetic head and the magnetic recording medium. By 1000
A / m.
When the magnetic field applied to the magnetic layer 12 is reversed, not only the magnetization of the magnetic layer 14 but also the direction of the magnetization of the magnetic layer 12 changes (reversed).

Since a material having a relatively low coercive force is used for the magnetic layer 12, the influence of the leakage magnetic field from the magnetic layer 12 is small, and the coercive force and the anisotropic magnetic field of the magnetic layer 14 are reduced. Hoshino et al.'S report (Japanese Journal of Applie
d Physics, Vol. 34, No. 3, 1526-1533
As shown in (Page), when a material having a high coercive force is used for the magnetic layer 12, the coercive force of the magnetic layer 14 increases, and this type of multilayer film cannot be used for a magnetoresistive head.

FIG. 2 is a view for explaining the directions of easy magnetization of the two magnetic layers 12 and 14 in the multilayer film 10 shown in FIG.
FIG. 2A is a schematic plan view of the magnetic layer 12, and FIG. 2B is a schematic plan view of the magnetic layer 14 formed above the magnetic layer 12. When a magnetoresistive element having this multilayer film is used for a reproducing head of a magnetic head, it is assumed that the sliding surface of the head is located below the magnetic layers 12, 14 shown in FIGS. 2 (a) and 2 (b). I do. Further, the leakage magnetic field from the recording magnetization of the magnetic recording medium is applied to the magnetic layers 12 and 14 in the multilayer film from a direction perpendicular to the head sliding surface.

The direction A of easy magnetization of the magnetic layer 12 having the higher coercive force is a direction parallel to the direction of the leakage magnetic field from the recording magnetization of the magnetic recording medium. Therefore, when a magnetic field exceeding the coercive force is applied in a direction opposite to the magnetization direction of the magnetic layer 12, the magnetization of the magnetic layer 12 is reversed. On the other hand, the easy magnetization direction B of the magnetic layer 14 is a direction perpendicular to the direction of the leakage magnetic field from the recording magnetization of the magnetic recording medium. Therefore, the magnetic field for reversing the magnetization of the magnetic layer 14 is an anisotropic magnetic field. Such arrangement and combination of the magnetic layers is preferable in that a magnetic field from a magnetic recording medium at a high frequency is detected. The anisotropic magnetic field of the magnetic layer 14 is smaller than the coercive force of the magnetic layer 12.

Next, a magnetic recording / reproducing method according to the present invention will be described with reference to FIGS. FIG. 3A is a diagram schematically showing recording magnetizations 51 to 55 recorded on the perpendicular magnetic recording medium 50, and FIG. 3B is a diagram showing the multilayer film 10 shown in FIG. FIG. 3C illustrates a change in the magnetization state of the magnetic layer 12 and the magnetic layer 14 when the read head incorporating the provided magnetoresistive element is relatively moved. FIG. 3C illustrates the output of the read head. It is. FIG.
FIG. 2 is a diagram showing a relationship between an applied magnetic field and an amount of voltage change between electrodes of a read head incorporating a magnetoresistive element including the multilayer film 10 shown in FIG.

Now, when an upward leakage magnetic field from the recording magnetization 51 of the magnetic recording medium 50 is applied to the reproducing head incorporating the magnetoresistive element having the multilayer film 10,
As shown in the left end of FIG. 3B, the magnetic layers 12 and 14 in the multilayer film 10 are both magnetized in the direction of the leakage magnetic field from the recording magnetization 51. At this time, the magnetic layers 12, 1
4 are parallel to each other, the magnetic resistance of the multilayer film 10 is small, and the output from the reproducing head is small as shown by a in FIG. The reproduction head records the magnetization 5 on the magnetic recording medium 50.
When moving from above the recording magnetization 52 to above the recording magnetization 52, there is no change in the magnetization direction of the magnetic layers 12 and 14. Therefore, FIG.
As shown in (c), there is no change in the output of the reproducing head.

Next, the read head is turned to the recording magnetization 52 facing upward.
Is moved from above to above the recording magnetization 53 whose magnetization has been inverted to downward magnetization. At this time, as shown in the lower part of FIG. 3B, only the magnetization of the magnetic layer 14 having a small anisotropic magnetic field is inverted downward by the influence of the leakage magnetic field from the recording magnetization 53, and the magnetic layer 14 having a large coercive force is obtained. The state in which the magnetization of the layer 12 remains upward, that is, the state in which the magnetization directions of the magnetic layers 12 and 14 are antiparallel is shown in FIG.
(B) As shown in the upper part, the magnetizations of the two magnetic layers 12 and 14 are both inverted downward due to the influence of the leakage magnetic field of the recording magnetization 53.

When the magnetizations of the magnetic layers 12 and 14 are antiparallel, the magnetoresistance of the multilayer film 10 shows a large value, and the output of the reproducing head increases as shown by b in FIG. The antiparallel state of the magnetizations of the magnetic layers 12 and 14 is a phenomenon that occurs temporarily when the leakage magnetic field applied to the magnetic layers 12 and 14 is reversed from the recording magnetization. When the leakage magnetic field from the recording magnetization 53 is sufficiently applied to the magnetic layers 12 and 14, the two magnetic layers 12 and 14
Are parallel and the magnetoresistance of the multilayer film 10 is c in FIG.
As shown by, the value again becomes small. Therefore,
As shown in FIG. 3C, a peak B appears in the output of the reproducing head corresponding to the portion where the recording magnetization is reversed.

Similarly, when the reproducing head moves from above the downwardly magnetized recording magnetization 54 to above the upwardly magnetized recording magnetization 55, as shown in the lower part of FIG. Only the magnetization of the small magnetic layer 14 is inverted upward by the influence of the leakage magnetic field from the recording magnetization 55,
3B, the magnetization of the magnetic layer 12 having a large coercive force remains downward, that is, the magnetization of the magnetic layers 12 and 14 is antiparallel. As described above, the magnetizations of the two magnetic layers 12 and 14 are both inverted upward under the influence of the leakage magnetic field of the recording magnetization 55.

Also in this case, when the magnetizations of the magnetic layers 12 and 14 are antiparallel, the magnetoresistance of the multilayer film 10 shows a large value, and the output of the reproducing head increases as shown by d in FIG. When a state in which an upward leakage magnetic field from the recording magnetization 55 is sufficiently applied to the magnetic layers 12 and 14 in the multilayer film 10 is obtained, the magnetizations of the two magnetic layers 12 and 14 both become upward. Since the magnetizations of the two become parallel, the magnetoresistance of the multilayer film 10 again takes a small value as shown by a in FIG. Therefore, the output of the reproducing head is shown in FIG.
As shown in (c), a peak D appears at a portion where the recording magnetization is reversed.

Thus, the output of the reproducing head is:
A peak corresponding to the reversal of the recording magnetization of the magnetic recording medium 50 appears. Therefore, a peak appearing in the output of the reproducing head is detected, and the peak is recorded on the magnetic recording medium by performing a process of associating the peak with a change in the polarity of the magnetic field applied from the recording medium, that is, the reversal of the recording magnetization of the magnetic recording. Information can be read.

FIG. 5 is a schematic block diagram of an example of a circuit for performing such signal processing. The output signal of the reproducing head 21 is input to a peak detector 22 that generates an output when the input signal exceeds a preset threshold. An output signal from the peak detector 22 is input to a synchronization detector 23 to which a frequency signal generated from a constant frequency signal generator 24 such as a clock is input. In the synchronization detector 23,
When the output is supplied from the peak detector 22 in synchronization with the frequency signal supplied from the constant frequency signal generator 24,
It is assumed that the sign of the signal recorded on the magnetic recording medium is inverted, and the peak detector 22 is synchronized with the frequency signal.
Is not supplied, it is assumed that the sign of the signal recorded on the magnetic recording medium is not inverted.
The output from the synchronization detector 23 is supplied to a signal reproducing circuit 25, and the signal reproducing circuit 25 reproduces the signal recorded on the magnetic recording medium from the information on the inversion and non-inversion of the code. Here, the peak detector 22, the synchronization detector 23
The constant frequency signal generator 24 constitutes a determination circuit 26 for determining whether the sign of the signal recorded on the magnetic recording medium has been inverted.

A magnetic head was manufactured using the magnetoresistance effect element according to the present invention. FIG. 6 is a partially cutaway perspective view of a read / write separation type head incorporating the magnetoresistive element of the present invention. The portion where the multilayer film 31 is sandwiched between the shield layers 32 and 33 functions as a reproducing head, and the portion of the lower magnetic pole 35 and the upper magnetic pole 36 which sandwich the coil 34 functions as a recording head. For the electrode 38, a material having a multilayer structure of Cr / Cu / Cr was used.

Hereinafter, a method for manufacturing this head will be described. A
A sintered body mainly composed of l ₂ O ₃ .TiC was used as a slider substrate 37. Shield layers 32 and 33, recording magnetic poles 35,
For 36, a Ni-Fe alloy formed by a sputtering method was used. The thickness of each magnetic layer was as follows. The upper and lower shield layers 32 and 33 were 1.0 μm, the lower magnetic pole 35 and the upper magnetic pole 36 were 3.0 μm, and Al ₂ O ₃ formed by sputtering was used as a gap material between the respective layers. The thickness of the gap layer is 0.2 mm between the shield layer and the magnetoresistive element.
μm, and 0.4 μm between the recording magnetic poles. Further, the distance between the reproducing head and the recording head was about 4 μm, and this gap was also formed of Al ₂ O ₃ . The coil 34 has a thickness of 3 μm C
u was used.

Using the above magnetic head, a magnetic recording / reproducing apparatus schematically shown in FIG. 7 was manufactured. FIG. 7A is a schematic plan view of the device, and FIG. 7B is a schematic longitudinal sectional view. This magnetic recording / reproducing apparatus includes a magnetic recording medium 41, a driving unit 42 for rotating the magnetic recording medium 41, a magnetic head 43 and its driving means 44, and a recording / reproducing signal processing means 45 for the magnetic head. This is a magnetic storage device having a configuration.

The magnetic recording medium 41 is a perpendicular magnetic recording medium, and is made of a Co-Cr-Pt alloy having a residual magnetic flux density of 0.75T. The track width of the magnetic head 43 was 1.5 μm. In the recording / reproducing signal processing system 45, the polarity of the magnetic field from the magnetic recording medium was changed when the voltage between the electrodes of the magnetoresistive head reached a certain level or higher.

By employing the above-described method of the present invention, a multilayer film having excellent soft magnetic characteristics and exhibiting a high rate of change in magnetoresistance can be used for a magnetic head for a magnetic recording / reproducing apparatus. A magnetic recording / reproducing apparatus having a recording density approximately six times higher than that using a resistance effect type head can be easily realized.

[0030]

According to the present invention, the difference in coercive force is small.
Since different types of magnetic layers can be used and the coercive force of the magnetic layer with the higher coercive force can be relatively low, a high-sensitivity magnetoresistive head can be obtained without impairing the soft magnetic characteristics of the magnetic layer it can. Further, a high-performance magnetic recording / reproducing apparatus can be obtained by using this magnetoresistive head.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of a multilayer film according to the present invention.

FIG. 2 is a view for explaining directions of easy magnetization of two magnetic layers in a multilayer film.

FIG. 3 is a diagram for explaining a magnetic recording / reproducing method according to the present invention.

FIG. 4 is a diagram showing a relationship between a magnetic field applied to a magnetoresistance effect element according to the present invention and a voltage change between electrodes.

FIG. 5 is a block diagram illustrating an example of a signal processing circuit.

FIG. 6 is a perspective view showing the structure of a magnetic head.

FIG. 7 is a schematic diagram of a magnetic recording and reproducing device.

[Explanation of symbols]

10 multilayer film, 11 substrate, 12, 14 magnetic layer, 13
... non-magnetic layer, 21 ... reproducing head, 22 ... peak detector,
23: Synchronous detector, 24: Constant frequency signal generator, 25
... signal reproduction circuit, 26 ... determination circuit, 31 ... multilayer film, 3
2, 33 ... shield layer, 34 ... coil, 35 ... lower magnetic pole, 36 ... upper magnetic pole, 37 ... substrate, 38 ... electrode, 41 ...
Magnetic recording medium, 42: magnetic recording medium drive unit, 43: magnetic head, 44: magnetic head drive unit, 45: recording / reproducing signal processing system

Claims (3)

(57) [Claims] 2. The magnetic recording medium according to claim 1 , wherein said magnetic recording medium has different coercive forces.
The magnetization can be reversed by the direction of the magnetic field applied from
The first magnetic layer and the second magnetic layer are stacked with the non-magnetic layer interposed therebetween.
Using a multi- layer film, and applying a magnetic field applied to the multi-layer film from a magnetic recording medium .
When the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are both reversed, the angle formed by the magnetization of the first magnetic layer and the magnetization of the second magnetic layer temporarily changes. A magnetic recording / reproducing method comprising detecting a change in magnetoresistance of the multilayer film due to being antiparallel. 2. The magnetic recording / reproducing method according to claim 1 , wherein the reversal of the recorded magnetization recorded on the magnetic recording medium is detected when the magnetic resistance of the multilayer film exceeds a predetermined value. Magnetic recording and reproducing method. 3. A magnetic head comprising a magnetic recording medium, recording medium driving means for driving the magnetic recording medium, a signal recording unit and a signal reproducing unit, a magnetic head driving means for driving the magnetic head, A magnetic recording / reproducing apparatus including a magnetic head recording / reproducing signal processing unit, wherein the magnetic head has a different coercive force as the signal reproducing unit.
Both have the direction of the magnetic field applied from the magnetic recording medium.
Therefore, the first magnetic layer and the second
A recording / reproducing signal processing unit that prints the multilayer film from a magnetic recording medium.
The magnetization of the first magnetic layer and the second
When the magnetizations of the magnetic layers are both reversed, the magnetization of the first magnetic layer
Angle between the magnetization and the magnetization of the second magnetic layer is temporarily antiparallel
Detection signals from the signal reproducing section due to become able to is characterized in that it comprises a determination means for the sign of the signal in which the recorded on the magnetic recording medium when exceeding a predetermined value is inverted Magnetic recording and reproducing device.