JP2000268323A - Magnetoresistive magnetic head and magnetic recording / reproducing apparatus having the same - Google Patents

Abstract

[PROBLEMS] To improve the sensitivity of a tunneling type magnetoresistive element when a multilayer film in which three magnetic layers are separated by two insulating layers is used. A magnetic layer (1) on both sides of two insulating layers (14, 15).
Voltage applying sections 16 and 17 are provided between the magnetic layers 1 and 12 and the magnetic layers 12 and 13, respectively, to apply a constant voltage, and the currents tunneling through the two insulating layers 14 and 15 are detected by the current detecting sections 18 and 19, respectively. The measurement was performed independently. [Effect] Even when the magnetizations of the two magnetic layers at both ends are reversed independently, reproduction corresponding to the situation is possible, and therefore, a magnetic recording / reproducing apparatus having a very high recording density. Can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive head and a magnetic recording / reproducing apparatus having the same, and more particularly to a reproducing magnetic head having high sensitivity and a magnetic recording / reproducing apparatus having the same.

[0002]

2. Description of the Related Art With the increase in density of magnetic recording, as a future reproducing magnetic head, a magazine by Julliere, Physics Letters, Vol. 54A.
(1975), Issue 3, p. 225, `` Tunneling between Ferromagnetic F
The application of the multilayer film exhibiting the magnetic tunneling phenomenon described in “ilms)” to a magnetoresistive head is being studied.

This multilayer film is formed by laminating a magnetic layer, an insulating layer, and a magnetic layer in this order. The multilayer film has a sandwich structure in which an insulating layer is sandwiched between two magnetic layers. When the electrons tunneling through the insulating layer enter the other magnetic layer, the tunnel probability changes depending on the direction of magnetization of the two magnetic layers. This change in tunnel probability is observed as a magnetoresistance effect.

Various types of multilayer films exhibiting the magnetic tunneling phenomenon have been studied. Abstracts by Kubota et al.
of 3rd International Symposium on Metallic Multila
yers, page 432 (1998), "Tunnel Magnetor
esistance in Junctions with Multilayered Barrier ''
It has been found that a multi-layer film in which three magnetic layers are separated by two insulating layers as shown in Fig. 3 may have a lower tunnel resistance when a voltage is applied to the two magnetic layers at both ends. ing.

The Japanese Journal of Ohno et al.
Applied Physics, Vol. 66, No. 5, pp. 1261 (1997)
`` Enhanced Magnetic Valve Effect and Magne
to-Coulomb Oscillations in Ferromagnetic Single El
It has been reported that when two multilayer films exhibiting magnetic tunneling phenomena are connected in series like an "ectron Transistor" and a certain potential is applied to the connection portion, the magnetoresistance change rate of the multilayer film increases.

[0006]

In the multilayer film reported by Kubota et al., A voltage is applied between the two magnetic layers at both ends of the three magnetic layers. Even if the reversal of the magnetization of the magnetic layers is performed independently, it is difficult to detect the reversal.

Further, when a multilayer film exhibiting two magnetic tunneling phenomena is connected like a multilayer film reported by Ohno et al., The connection portion becomes longer, and the size of the magnetoresistive effect element becomes larger. However, there is a problem that information on a magnetic recording medium recorded at a very high density cannot be reproduced.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned conventional problems, and to reduce the size of a magnetoresistive element having three magnetic layers utilizing the magnetic tunneling phenomenon and to perform high-density recording. It is an object of the present invention to provide a high-sensitivity magnetoresistive magnetic head suitable for reproducing information on a magnetic recording medium, and a magnetic recording / reproducing apparatus including the same.

[0009]

Means for Solving the Problems The inventors of the present invention have developed a magnetic layer using a multilayer film in which three magnetic layers are separated by two insulating layers by alternately laminating magnetic layers and insulating layers. As a result of intensive studies on the resistance effect type magnetic head, a constant voltage is applied between the magnetic layers on both sides of the two insulating layers, and a current that tunnels through the two insulating layers by an external magnetic field such as a magnetic recording medium. , As independent output signals, it was found that a reproducing magnetoresistive head suitable for high-density magnetic recording could be realized.

In a magnetoresistive effect element using a multilayer film in which three magnetic layers are separated by two insulating layers, when different magnetic fields are applied to the two magnetic layers at both ends, the two magnetic layers at both ends are removed. The magnetization reversals of the magnetic layers of the layers occur independently. In this case, according to the conventional technique, a voltage is applied only between the two magnetic layers at both ends, and a current flowing between the two magnetic layers at both ends is measured. It has been found that even if the magnetization reversals of each of the above occur independently, the situation cannot be detected. This is because the combined value of the current that tunnels through the two insulating layers is measured.

On the other hand, in the magnetoresistive head according to the present invention, since the currents tunneling through the two insulating layers are measured independently, the reversal of the magnetization of the two magnetic layers at both ends is independently performed. Even when the reproduction is performed, reproduction corresponding to the situation can be performed.

That is, the present invention has been made on the basis of such findings, and the object is to form a magnetic layer and an insulating layer alternately so that three magnetic layers are two insulating layers. A magneto-resistance effect type magnetic head using a separated multilayer film, wherein a means for independently applying a constant voltage between magnetic layers on both sides of the two insulating layers; and This is attained by a magnetoresistive effect type magnetic head comprising: current detection means for independently detecting a current tunneling through a layer as an output signal.

When the three magnetic layers are formed into a first magnetic layer, a second magnetic layer, and a third magnetic layer in the order of lamination,
The first and third magnetic layers, which are two layers at both ends, are configured to be applied with magnetic fields from different magnetic domains adjacent to each other in the magnetic recording medium as the external magnetic field. The effect type magnetic head can reproduce information on a magnetic recording medium recorded at a very high density with high sensitivity.

Further, since the magnetoresistive head of the present invention uses a multilayer film in which three magnetic layers are separated by two insulating layers, the size thereof is small, and recording is performed at high density. It is suitable for reproducing information on a magnetic recording medium.

Although the magnetoresistive effect type magnetic head is exclusively for reproduction, if it is combined with a well-known inductive type magnetic head, it can be easily formed as a recording / reproducing magnetic head. Therefore, if this recording / reproducing magnetic head is applied to a magnetic recording / reproducing device, a high-performance magnetic recording / reproducing device can be easily realized.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the schematic diagram of FIG. 1 schematically showing a magnetic head of the present invention. Magnetic head 1 using multilayer film
0 is the first magnetic layer 11 / the first insulating layer 14, the second magnetic layer 1
2 / second insulating layer 15 / third magnetic layer 13 in this order,
It is composed of a laminated film of three magnetic layers and two insulating layers. Then, a first voltage applying unit 16 is provided between the first magnetic layer 11 and the second magnetic layer 12 to apply a constant voltage. Further, a second voltage applying unit 17 is provided between the second magnetic layer 12 and the third magnetic layer 13 to apply a constant voltage.

Further, between the first magnetic layer 11 and the first voltage applying section 16, a current detecting section 18 for detecting a current tunneling through the first insulating layer 14 is provided. Also, the third
A current detector 19 for detecting a current tunneling through the second insulating layer 15 is also provided between the magnetic layer 13 and the second voltage applying unit 17. The current detectors 18 and 19 are configured to be able to independently detect currents tunneling through the insulating layers 14 and 15, respectively.

The first and second voltage applying units 16 and 17
Normally, both are set to the same voltage value in a DC constant voltage power supply, but may be different voltage values depending on the purpose of use. A preferable DC voltage is 0.01 to 0.1 V. Further, the power supply is not necessarily a DC constant voltage power supply, and may be other than DC, such as an AC or a pulse current, depending on circumstances.

The first magnetic layer 11 and the third magnetic layer 13 are made of, for example, a Ni—Fe alloy, a Ni—Fe—Co alloy,
-Film thickness of 5 to 30 nm with good soft magnetic properties such as Fe-based alloys
And the second magnetic layer 12 is, for example,
A magnetic film having a high coercive force and a film thickness of 8 to 20 nm, such as a Co-Pt alloy, a Co-Cr alloy, or a Co-Ta alloy, is used.

As the insulating layers 14 and 15, for example,
Insulation barrier height of Al oxide (Al ₂ O ₃ ), other MgO etc. is 1.
An insulating thin film with a thickness of about 5 to 2.5 eV and a thickness of about 0.6 to 2.5 nm can be used. The insulating barrier height of Al ₂ O ₃ is 2 eV, and MgO is 1.5 eV.

The laminated film of the magnetic layer and the insulating layer can be easily formed by a known film forming technique, for example, a sputtering method.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. <Embodiment 1> As shown in FIG. 1, a magnetic head 10 has a first magnetic layer 11, a first insulating layer 14, a second magnetic layer 12,
A multilayer film is formed in the order of the insulating layer 15 and the third magnetic layer 13, and a constant voltage is applied between the first magnetic layer 11 and the second magnetic layer 12 by the first voltage applying unit 16. Further, a constant voltage is applied between the second magnetic layer 12 and the third magnetic layer 13 by the second voltage applying unit 17.

A current detecting section 18 between the first magnetic layer 11 and the first voltage applying section 16 and a current detecting section 19 between the third magnetic layer 13 and the second voltage applying section 17 are provided. Thus, currents tunneling through the insulating layers 14 and 15 can be detected independently.

In this embodiment, the first magnetic layer 11 and the third
For the magnetic layer 13, a Ni-20at% Fe alloy with a thickness of 15 nm was used, and for the second magnetic layer 12, a Co-17at% Pt alloy with a thickness of 8 nm was used. The insulating layers 14 and 15 each have a thickness of 1.3 nm.
Al oxide (Al ₂ O ₃ ) was used. The applied voltages of the voltage applying units 16 and 17 are each 0.05 V. Each of the magnetic layer and the insulating layer was formed by a well-known sputtering method.

As shown in FIG. 1, the magnetoresistive magnetic head 10 is moved closer to the magnetic recording medium 21. As shown
The magnetization of the first magnetic layer 11 is directed upward by the magnetic domains 22 of the magnetic recording medium 21. The third magnetic layer 1 is formed by the adjacent magnetic domains 23.
The magnetization of 3 points downward. Since the second magnetic layer 12 has a high coercive force, the direction of magnetization of the magnetic layer 12 does not change. In this embodiment, the magnetization of the second magnetic layer 12 is upward.

In magnetic tunneling, when the magnetization directions of the magnetic layers on both sides of the insulating layer are parallel, a large amount of current tunnels through the insulating layer. The current that tunnels through the layers is small. Therefore, at the position of FIG. 1, the current that tunnels through the first insulating layer 14 is large, and the current that tunnels through the second insulating layer 15 is small.

From this, the current detectors 18 and 19
As a result, the current that tunnels through the first insulating layer 14 and the second
By detecting the current that tunnels through the insulating layer 15,
It can be seen that information recorded on the magnetic recording medium 21 can be read.

In a state where the magnetoresistive head 10 and the magnetic recording medium 21 are sufficiently close to each other, the total thickness of the multilayer film and the length of two bits in recording are almost the same, so that the density is extremely high. It becomes possible to read the recorded information.

In the case of this embodiment, the total thickness of the multilayer film is 40.6.
nm, the length of one bit is about 20 nm. This corresponds to a linear recording density of 1.265 MBPI. In this study, the magnetic domain state of a magnetic recording medium in which magnetic clusters having a diameter of about 20 nm were dispersed in an insulator was actually read by the above-described magnetoresistive head. As a result of this principle experiment,
With the above-mentioned magnetoresistive effect type magnetic head, it is possible to read the magnetic domain state of the magnetic recording medium, and if a magnetic recording medium capable of high-density recording is obtained, it is understood that a linear recording density of 1.265 MBPI can be achieved. Was.

As shown in FIG. 1, when the magnetoresistive head moves in the direction of travel 24, the magnetic domain 23
Can be detected again by the direction of magnetization of the first magnetic layer 11. In this method, the same information can be read twice, and the information can be reliably reproduced.

In this embodiment, the first magnetic layer 11 and the third
Although a Ni-20at% Fe alloy was used as the material for the magnetic layer 13, the materials for the magnetic layers 11 and 13 only need to exhibit good soft magnetic characteristics, and other materials can be used. Other materials include Ni-Fe alloys of other compositions, N
There are i-Fe-Co alloys, Co-Fe alloys and the like.

In the present embodiment, the Co-17 at% Pt alloy is used as the material of the second magnetic layer 12, but the material of the magnetic layer 12 only needs to show a high coercive force, and other materials may be used. It is possible. Other materials include Co-Pt alloys, Co-Cr alloys, and Co-Ta alloys having other compositions.

Further, the magnetoresistive head shown in this embodiment has no recording capability. Therefore, in order to perform recording and reproduction, it is necessary to use it in combination with an inductive magnetic head for recording.

Embodiment 2 A magnetic disk drive was manufactured using the magnetoresistive head 10 of the present invention described in Embodiment 1. FIG. 2 shows the main structure of the device. FIG. 2 (a)
2 is a plan view, and FIG. 2B is a cross-sectional view taken along line AA ′ of FIG. 2A. For the magnetic recording medium 31 rotated by the magnetic recording medium drive unit 32, a magnetic material made of a Co-Cr alloy was used. The track width of the magnetic head 33 held by the magnetic head drive unit 34 was 1 μm.

In the magnetic recording / reproducing apparatus using the magnetoresistive head of the present invention, a high output reproduced signal was observed. This is because the magnetoresistive head of the present invention exhibits a high magnetoresistance change.

When a reproduction principle experiment was performed using a magnetic recording medium in which Co having an average particle diameter of 20 nm was dispersed in an insulator made of silicon dioxide, it was found that the magnetization of Co particles could be sufficiently detected. It was found that if a magnetic recording medium capable of high-density recording could be obtained, a linear recording density of 1.265 MBPI could be achieved.

[0037]

As described in detail above, the intended object has been achieved by the present invention. That is, in a magnetoresistive head using a multilayer film in which three magnetic layers are separated by two insulating layers, means for applying a constant voltage to the magnetic layers on both sides of the two insulating layers, By providing means for independently measuring currents tunneling through the two insulating layers, it is possible to obtain a reproducing magnetoresistive head suitable for high-density magnetic recording. Further, by using the magnetoresistive head of the present invention, a magnetic recording / reproducing apparatus having an extremely high recording density can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration and a principle of reproduction of a magnetoresistive head according to the present invention.

FIG. 2 is an explanatory diagram showing a main part structure of the magnetic disk drive of the present invention.

[Explanation of symbols]

 10 ... magnetic head, 11,12,13 ... magnetic layer, 14,15 ... insulating layer, 16,17 ... voltage applying part, 18,19 ... current detecting part, 21 ... magnetic recording medium, 22,23 ... magnetic domain, 24 ... Magnetoresistance effect type traveling direction, 31 ... Magnetic recording medium, 32 ... Magnetic recording medium drive unit, 33 ... Magnetic head, 34 ... Magnetic head drive unit, 35 ... Recording / reproduction signal processing system.

Claims (4)

[Claims] 1. A magnetoresistive effect type magnetic head using a multilayer film in which magnetic layers and insulating layers are alternately stacked, and three magnetic layers are separated by two insulating layers. A means for independently applying a constant voltage between the magnetic layers on both sides of the two insulating layers; and a current detecting means for independently detecting a current tunneling through the two insulating layers by an external magnetic field as an output signal. A magnetoresistive head. 2. The method according to claim 1, wherein the three magnetic layers are formed in the order of lamination.
When the magnetic layer, the second magnetic layer, and the third magnetic layer are used, a magnetic field from an adjacent different magnetic domain of the magnetic recording medium serving as the external magnetic field is applied to the first and third magnetic layers at the two ends, respectively. 2. The magnetoresistive head according to claim 1, wherein said magnetic head is of a structure to be formed. 3. A recording / reproducing magnetic head comprising a combination of the magnetoresistive head of claim 1 or 2 and an inductive magnetic head. 4. A magnetic recording / reproducing apparatus comprising the magnetic head according to claim 1.