JPH06282802A - Magnetic recorder-reproducer - Google Patents

Abstract

PURPOSE:To suppress waveform distortion and Barkhausen noise by a method wherein a bias in the lateral or longitudinal direction is impressed on a magnetoresistance effect type head from a lower magnetic layer of a magnetic recording medium. CONSTITUTION:A magnetic disk as a magnetic recording medium has a construction of a magnetic double layer formed of a laminate of a lower magnetic layer 21, an upper magnetic layer 22 and a magnetic isolating layer 20 inserted between these two magnetic layers. The lower magnetic layer 21 is prepared by forming a hard film of CoPt on a glass base 23 so that the axis of easy magnetization is directed in the vertical direction. The upper magnetic layer 22 is constituted of Co-Cr-Ta and has this axis in an in-plane direction. The isolating layer 20 is constituted of Cr and interrupts magnetic coupling of the upper magnetic layer 22 and the lower magnetic layer 21. The lower magnetic layer 21 is magnetized beforehand in the upward or downward direction in respect to the thickness and a lateral bias is impressed on an MR head by a leakage flux generated from this layer.

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 device such as a magnetic disk device or a magnetic tape device using a reproducing head having a magnetoresistive effect, and more particularly to a structure for applying a bias magnetic flux to a magnetoresistive thin film element.

[0002]

2. Description of the Related Art As a conventional magnetic recording / reproducing apparatus, a recording / reproducing separated type in which a recording operation is an inductive thin film head and a reproducing operation is a magnetoresistive head is often used. Among them, the magnetoresistive head (hereinafter referred to as MR head) utilizes the property that the electric resistance value is changed by an applied magnetic field in a thin film (hereinafter referred to as MR film) having a magnetoresistive effect such as Ni ₈₀ Fe _20. Is a magnetic head for reading out magnetization information from a magnetic recording medium, and has a higher reproduction sensitivity than an inductive magnetic head, and since the reproduction output does not depend on the peripheral speed of the magnetic disk, the density of the magnetic recording device can be increased. The device is advantageous for miniaturization.

Since the relationship between the resistivity (ρ) of the MR film and the applied magnetic field (H) has non-linearity, when it is used as a head, an appropriate bias is applied in the lateral direction. It is necessary to design to operate in the linear region and in the region where the inclination is as large as possible. The above-mentioned means for linearization is called lateral bias, and many methods are known, but the soft film bias method will be described as a first conventional example with reference to FIG. The MR head using the soft film bias method is C
o A soft film 3 made of amorphous material, a spacer 2 made of a non-magnetic material, and an MR film 1 are sequentially laminated, and electrodes 61 are provided at both ends of a sense region 51 for sensing a magnetic signal recorded in a magnetic layer on a magnetic recording medium. , 62 are formed. A sense current Is flowing through the MR film 1 in the sense region magnetizes the soft film 3 therebelow, and a leakage magnetic flux H applies a lateral bias to rotate the magnetization vector M of the MR film to about 45 °. . In this state, the leakage magnetic flux from the recording magnetization of the magnetic recording medium is detected to obtain an output signal.

As a second conventional example, there is a hard film bias method. In this method, a hard film layer made of CoPt or the like is arranged close to the MR film, and a lateral bias is applied by the leakage magnetic flux. Next, as a countermeasure against noise, a third conventional example will be described. In reproduction using a magnetoresistive head, there is a problem of so-called Barkhausen noise, in which irregular jumps and distortions occur in the reproduction waveform. This is due to the movement of the domain wall in the MR film, and as a method for suppressing this, an antiferromagnetic film made of Fe-Mn or the like or C on the MR film.
A technique is known in which a ferromagnetic film made of o-Pt or the like is formed and the MR film is made into a single magnetic domain by using an exchange coupling magnetic field or a leakage magnetic field in the track direction at the interface. Such a technique is called longitudinal bias. FIG. 5 shows a sectional view of an MR head having a third conventional structure. The soft film 3, the spacer 2 and the MR film 1 are laminated, and the antiferromagnetic layers 14 and 15 and the electrodes 61 and 62 are formed at the ends of the sense region 51. The soft current is magnetized by the sense current flowing in the MR layer, and a lateral bias is applied by the leakage magnetic flux to linearize the soft film. Further, the longitudinal bias is applied by the exchange coupling magnetic field at the interface between the antiferromagnetic layer and the MR layer, so that the MR film is made into a single magnetic domain, and Barkhausen noise due to the domain wall movement during reproduction is reduced. As described above, the first, second and third conventional examples have a structure in which the head itself has a means for applying a lateral bias or a longitudinal bias to the magnetoresistive head, and the magnetic layer of the magnetic recording medium is Only one layer for data recording.

Next, as a fourth conventional example, a recording method using a magnetic recording medium having a magnetic double layer will be described with reference to FIG. The magnetic layer includes a lower magnetic layer 31 for recording servo signals from below, a separation layer 30 for blocking magnetic coupling between the lower magnetic layer and the upper magnetic layer, and an upper magnetic layer 32 for recording data signals. It has a magnetic double layer structure, and both the upper magnetic layer and the lower magnetic layer are films having an easy axis of magnetization in the plane. On the other hand, the head has two heads
One is an MR head 10 for reading a servo signal, and the other is an inductive type / MR type composite head 11 for reading a data signal. With this structure, the servo signal from the lower magnetic layer 31 is read by the head 10, and the data signal from the upper magnetic layer 32 is read and written by the head 11. The interference of each signal is caused by providing the separation layer 30 and
Can be prevented by tilting. As described above, the purpose of forming the magnetic double layer in the fourth conventional example is to record a servo signal, and there is no known example as a bias means.

[0006]

As described above, the conventional M
In the soft film bias method as a lateral bias application method for the R head, the bias is not applied uniformly in the film thickness direction of the MR film, which causes waveform distortion, or when the nonmagnetic layer 2 is a conductor, a shunt bias effect. As a result, the uniformity of the bias is increased, but there is a problem in that the sense current is shunted to the non-magnetic layer side, the output is reduced, and the heat generated in the conductor layer is easily affected. Further, in the lateral bias application by the hard film method, there is a problem that the magnetization state of the film is different due to the difference in the composition of the hard film, the film forming conditions, etc., and it is difficult to control. Regarding the longitudinal bias application method, the corrosion resistance of the Fe-Mn antiferromagnetic film is poor.
In a ferromagnetic film, there are two types of bias components, an exchange coupling magnetic field and a leakage magnetic field, which makes it difficult to optimally control the bias magnetic field. Barkhausen noise could not be suppressed sufficiently. Further, in any of the configurations, the head itself has a means for applying a lateral bias and a longitudinal bias, which complicates the structure and causes yield deterioration.

[0007]

According to the present invention, by combining a magnetoresistive effect head and a magnetic recording medium having a magnetic double layer, a lower magnetic layer magnetized in the thickness direction in advance is converted into a magnetoresistive head. A lateral bias is applied, or a longitudinal bias is applied to the magnetoresistive head by a lower magnetic layer magnetized in advance in the running direction of the magnetic recording medium to operate.

[0008]

The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, which is intended for a magnetic disk as a magnetic recording medium. In FIG. 1, the magnetic disk has a magnetic double layer structure, and the glass substrate 2
A lower magnetic layer 21 (coercive force: Hc = 2000 Oe, film thickness: t = 0.5 μm) in which a hard film made of CoPt is formed on the magnetic layer 3 so that the easy axis of magnetization is oriented in the vertical direction, C
The upper magnetic layer 22 (Hc = 1500 Oe, t = 0.03 μm) made of o-Cr-Ta and having an easy axis in the in-plane direction.
m), a separation layer 20 sandwiched between the upper magnetic layer and the lower magnetic layer made of Cr for blocking magnetic coupling.
(T = 0.1 μm). Each is continuously formed by the sputtering method. The head is a magnetoresistive film 1 (t = t) made of permalloy on a ceramic substrate.
0.08 μm), electrodes 61 and 6 made of tungsten
2 is patterned by ion milling after sputtering formation. If necessary, a shield layer made of a soft magnetic material such as permalloy may be formed on the upper and lower sides of the MR element through a gap made of a nonmagnetic material such as alumina. After that, an inductive type thin film magnetic head element is formed on the upper portion by a known method. In FIG. 1, the lower magnetic layer is magnetized in the upward or downward direction with respect to the thickness in advance, and the magnetization of the MR film is rotated by the leakage magnetic flux generated from this layer to apply a lateral bias. In this state, recording / reproducing is performed by the composite head. During writing, the magnetic flux generated by the inductive thin film head causes magnetization rotation only in the upper magnetic pole layer 22, has a larger coercive force, and does not affect the lower magnetic pole layer 21 at a distance. In FIG. 2, the lower magnetic layer is magnetized upward once, and after writing a certain number of times in the inductive head in the same track, the bias magnetic field at the time of reading is measured.
Even after 000 times, the rate of change in the bias magnetic field was 5% or less, which was a practically no problem level.

Next, a second embodiment will be described with reference to FIG. In FIG. 3, the magnetic recording medium is a magnetic disk and has a magnetic double layer structure. The magnetic recording medium has an easy axis of in-plane magnetization on a glass substrate and is pre-magnetized in the track direction.
The lower magnetic layer 41 made of Pt (Hc = 2000 Oe, t
= 0.5 μm), an upper magnetic layer 42 (Hc = 1500 Oe, made of Co—Cr—Ta and having an easy axis in the in-plane direction).
t = 0.03 μm), and a separation layer 40 (t = 0.1 μm) sandwiched between the upper magnetic layer made of Cr and the lower magnetic layer for blocking magnetic coupling. Each is continuously formed by the sputtering method. Further, the head is a soft film 3 made of a-Co, T
Spacer 2 made of a and MR film 1 made of permalloy
After forming (t = 0.08 μm) by sputtering, a pattern is formed by ion milling. Subsequently, electrodes 61 and 62 made of tungsten are provided outside the sense region 51 and, if necessary, on the upper and lower sides of the MR element via a gap made of a non-magnetic material such as alumina, and a shield made of a soft magnetic material such as permalloy. The layers may be patterned. After that, an inductive type thin film magnetic head element is formed on the upper portion by a known method (not shown). In this configuration, linearization is performed by the soft film method. Further, a leakage magnetic flux from the lower magnetic layer applies a bias in the longitudinal direction to the MR film to form a single magnetic domain.

In the above second embodiment of the present invention, the frequency of occurrence of Barkhausen noise observed on the reproduced waveform from the MR head was measured. For comparison, a comparison was made with the configuration of the longitudinal bias method using an antiferromagnetic film given as the third conventional example. 10 dB and 1 for the signal (S) in the read state
The number of noises (N) exceeding the threshold voltage (Vth) of 5 dB was counted. The results are shown in Table 1. As described above, in the configuration of the present invention, the optimum bias can be applied and the suppression of Barkhausen noise can be significantly improved as compared with the related art. Furthermore, when a longitudinal bias by an antiferromagnetic film is applied in addition to this structure, noise can be further suppressed. The above is the embodiment for the magnetic disk device, but it goes without saying that the same effect can be obtained for the magnetic tape device.

[0011]

As described above, in the present invention, the optimum lateral bias is applied to the MR head by applying a lateral or vertical bias from the lower magnetic layer of the magnetic disk or magnetic tape which is the magnetic recording medium. A longitudinal bias can be applied, and a magnetic recording / reproducing apparatus with small waveform distortion and noise can be achieved. Further, the structure of the head is simplified and the yield is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention, in which a lateral bias is applied to an MR head from a magnetic recording medium.

FIG. 2 shows a result of measuring a bias magnetic field at the time of reading after the lower magnetic layer is magnetized upwardly once in the configuration of the present invention and after writing a certain number of times in the inductive head in the same track. It is a diagram showing.

FIG. 3 is a configuration diagram showing a second embodiment of the present invention, in which a longitudinal bias is applied to the MR head from the magnetic recording medium.

FIG. 4 is a schematic diagram of a configuration using a soft film bias method as a first conventional example.

FIG. 5 is an MR having an antiferromagnetic film of a third conventional example.
It is sectional drawing of a head.

FIG. 6 is a schematic view of a recording method using a magnetic recording medium having a magnetic double layer as a third conventional example.

[Explanation of symbols]

 1 MR Film 2 Spacer 3 Soft Film 10 MR Head for Servo 11 Induction Type / MR Composite Head for Data 14, 15 Antiferromagnetic Layer 20, 30, 40 Separation Layer 21, 31, 41 Lower Magnetic Layer 22, 32, 42 Upper Magnetic layer 23 Ceramic substrate 51 Sense area 61, 62 Electrode

Claims (3)

[Claims] 1. A magnetic recording medium having a magnetic double layer composed of a lower magnetic layer, an upper magnetic layer and a magnetic separation layer inserted between both magnetic layers, an induction type magnetic recording head and a magnetoresistive effect. Is a magnetic recording / reproducing apparatus which is used in combination with a composite type head having a magnetoresistive effect reproducing head using a thin film element showing the magnetoresistive effect, wherein the magnetization of the lower magnetic layer exhibits the magnetoresistive effect. A magnetic recording / reproducing apparatus characterized in that it is configured to apply a bias magnetic flux to the. 2. The magnetic recording according to claim 1, wherein the magnetization direction of the lower magnetic layer is the thickness direction of the lower magnetic layer, and a bias magnetic flux for rotating the magnetization vector of the thin film element in the hard axis direction is applied. -Playback device. 3. The magnetic recording / reproducing according to claim 1, wherein the magnetization direction of the lower magnetic layer is the running direction of the magnetic recording medium, and a bias magnetic flux is applied to make the magnetization of the thin film element a single magnetic domain in the longitudinal direction. apparatus.