JP3607815B2 - Magnetic head, double-layered perpendicular magnetic recording medium, and magnetic reproducing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high density perpendicular magnetic reproducing method using an active magnetic head using a double layer perpendicular magnetic recording medium and a high frequency signal.
[0002]
[Prior art]
In the field of magnetic recording, a longitudinal recording / reproducing system for recording on a longitudinal recording medium by a ring-type magnetic head on a magnetic tape or HDD has been performed. However, in this method, since the recording magnetization is recorded in the longitudinal direction, the demagnetizing field becomes larger as the recording signal has a shorter wavelength, and the recording density becomes harder to record. On the other hand, in the perpendicular magnetic recording system, magnetization is recorded in the perpendicular magnetic recording layer in the perpendicular direction by using a two-layer perpendicular magnetic recording medium comprising a perpendicular magnetic recording layer and a soft magnetic layer film and a single pole type head. Therefore, the demagnetizing field of the recording magnetization becomes smaller as the wavelength becomes shorter, and this is a recording method that is attracting attention for improving the recording density.
[0003]
That is, as shown in FIG. 6, the magnetic recording medium is a two-layer perpendicular magnetic recording in which a perpendicular recording layer 2 and a soft magnetic layer 3 (referred to as a backing layer) such as permalloy are formed on a substrate such as glass as its lower layer. A signal magnetic flux 9 in which a signal magnetization 10 recorded on the perpendicular recording layer 2 using a medium is reproduced by a single pole type magnetic head of the perpendicular head flows through the backing layer 3, that is, as if it is a closed magnetic circuit as a part of the head. Is forming.
[0004]
However, it is composed of a perpendicular magnetic recording layer and a soft magnetic layer, and in particular for a disturbance magnetic field in the horizontal direction, the magnetic flux 21 entering from the backing layer 3 which is a high permeability layer of the magnetic recording medium is applied to the single pole head. It was sucked up, differentiated by the whistle line 22, and detected as a noise component between the reproduction terminals 23 and 24. Since this soft magnetic layer has a high magnetic permeability and a large area, the magnetic field induced in the soft magnetic layer of this total area concentrates on a single pole, so that a large level of noise is picked up. is there.
[0005]
On the other hand, inductive heads such as ferrite heads, MIG heads, and thin film heads have been put to practical use as magnetic heads for hard disks (HDDs).
[0006]
In recent years, a magnetoresistive (MR) head has been put into practical use as a reproducing head. In such a head, when a disturbance DC magnetic field is applied from the outside, the symmetry of the waveform is lost and an error occurs in signal processing. This is called asymmetry.
[0007]
Further, FIG. 7 is reported in the IEICE Technical Report MR95-85, and an element and a head using a change in magnetic impedance are proposed. FIG. 7 shows the principle of operation of a magneto-impedance element in which a lead 25 made of a conductive metal thin film is sandwiched by 29 and 30 soft magnetic cores made of a laminated film of a permalloy film 27 and a SiO2 film 28 over a track width 26. is there. A high-frequency signal is applied from a UHF-band high-frequency transmitter 31 through a resistor 32 to energize a current 33, and between the terminals based on a change in magnetic impedance between terminals 34 and 35 arranged at both ends of the lead 25. It detects the voltage change. When there is no signal magnetic field generated from the magnetization 37 on the magnetic recording medium 36, a UHF carrier corresponding to the product of the current 33 and the impedance between the terminals 34 and 35 of the lead 25 is present between the terminals 34 and 35. When a signal voltage is generated and a signal magnetic field is received from a magnetic recording medium, the magnetization direction of the soft magnetic core of the element is oriented in the track width direction, so the magnetization is oriented by the signal magnetic field. Inclination from the direction decreases the magnetic impedance. Therefore, the UHF carrier signal is detected in the form of AM modulation by the signal magnetic field of the magnetic recording medium. The signal magnetization 37 on the magnetic recording medium 36 can be read out by AM detection of this signal. When this head is realized, it is expected that there is a possibility that an output about 10 times that of a giant MR head currently being developed can be obtained. FIG. 8 shows the operation curve of the element shown in FIG. That is, the high frequency voltages detected at the terminals 34 and 35 are plotted. A high frequency voltage detected at the terminals 34 and 35 is obtained by applying a dc magnetic field to the above element at the center of the Helmholtz coil with a carrier signal frequency of 1.0 GHz. When the value of the DC magnetic field is 0, the high frequency voltage detected at the terminals 34 and 35 is the largest. As the DC magnetic field is increased, the high-frequency voltage detected at the terminals 34 and 35 decreases. As can be seen from FIG. 8, this DC magnetic field corresponds to the signal magnetic field on the magnetic recording medium 36, and in order to reproduce the signal with high sensitivity and obtain a waveform with small distortion, it is necessary to set the DC bias 38 points. That is, when a DC magnetic field corresponding to 38 points is applied to the element, the voltage changes substantially linearly in the vicinity of 38 points, so that distortion is small. In the above model, a carrier signal and a direct current are passed through the lead 25 to generate a direct current magnetic field, which serves as a bias.
[0008]
[Problems to be solved by the invention]
As described above, it is desired to realize a high-density magnetic recording / reproducing method by using a two-layered perpendicular magnetic recording medium. However, as described above, the conventional two-layer recording medium is easy to induce noise, The magnetic head also has a problem that asymmetry is easily generated with respect to a disturbance magnetic field generated from a geomagnetism or a motor.
[0009]
The present invention takes into consideration the problem that such a conventional magnetic reproducing method is likely to induce noise, and is combined with the characteristics of an MI head that originally requires a DC bias to generate a disturbance magnetic field generated in a two-layer perpendicular magnetic recording system. It is an object of the present invention to provide a magnetic recording / reproducing method that effectively prevents noise caused by the above.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problem, a first aspect of the present invention (corresponding to claim 1) is formed by sandwiching a conductive thin film with a soft magnetic material, and two or more pairs of electrodes are formed at both ends of the conductive thin film. Magnetic reproducing method using a magnetic head in which terminals are arranged, a high frequency carrier signal current and a DC bias current are simultaneously applied to a first pair of electrode terminals, and a high frequency reproduction signal modulated by a recording magnetic field is reproduced from the second pair of electrode terminals In
When a two-layer perpendicular magnetic recording medium using a perpendicular recording layer and a soft magnetic layer film is to be reproduced, a DC magnetic field bias by the DC bias current is set to a value close to the coercive force of the soft magnetic layer film. This is a magnetic reproduction method.
[0011]
According to a second aspect of the present invention (corresponding to claim 2), a conductive thin film is sandwiched between soft magnetic materials, two or more pairs of electrode terminals are disposed on both ends of the conductive thin film, and the first pair In a magnetic reproducing method using a magnetic head, a high frequency carrier signal is applied to the electrode terminals of the magnetic head, a high frequency reproduction signal modulated by a recording magnetic field is reproduced from a second pair of electrode terminals, and a DC magnetic field bias is applied to the soft magnetic material. ,
When reproducing a dual-layer perpendicular magnetic recording medium using a perpendicular recording layer and a soft magnetic layer film,
The magnetic reproducing method is characterized in that the DC magnetic field bias is set to a value close to the coercive force of the soft magnetic layer film by a DC bias applying means formed in a part of the magnetic head.
[0012]
A third aspect of the present invention (corresponding to claim 3) is the magnetic reproducing method according to the first aspect or the second aspect, wherein the coercive force of the soft magnetic layer film is larger than the disturbance magnetic field. .
[0013]
According to a fourth aspect of the present invention (corresponding to claim 4), the soft magnetic layer film of the two-layered perpendicular magnetic recording medium is a laminated film composed of a metal magnetic layer film and an insulating layer film. A magnetic reproducing method according to any one of the first to third inventions.
[0014]
According to a fifth aspect of the present invention (corresponding to claim 5), a conductive thin film is sandwiched between soft magnetic materials, two or more pairs of electrode terminals are disposed at both ends of the conductive thin film, and the first pair A magnetic head that simultaneously applies a high-frequency carrier signal current and a DC bias current to the electrode terminals of the first and second high-frequency reproduction signals modulated by a recording magnetic field from the second pair of electrode terminals;
When a dual-layer perpendicular magnetic recording medium using a perpendicular recording layer and a soft magnetic layer film is to be reproduced, the DC magnetic field bias due to the DC bias current is set to a value close to the coercive force of the soft magnetic layer film. A magnetic head characterized by the following.
[0015]
According to a sixth aspect of the present invention (corresponding to claim 6), a conductive thin film is sandwiched between soft magnetic materials, two or more pairs of electrode terminals are disposed on both ends of the conductive thin film, and the first pair A magnetic head that applies a high-frequency carrier signal to the electrode terminals of the magnetic head, reproduces a high-frequency reproduction signal modulated by a recording magnetic field from the second pair of electrode terminals, and applies a DC magnetic field bias to the soft magnetic body;
When reproducing a double-layered perpendicular magnetic recording medium using a perpendicular recording layer and a soft magnetic layer film,
The magnetic head is characterized in that the DC magnetic field bias from the DC bias applying means formed in a part of the magnetic head is set to a value near the coercive force of the soft magnetic layer film.
[0016]
According to a seventh aspect of the present invention (corresponding to claim 7), a conductive thin film is sandwiched between soft magnetic materials, two or more pairs of electrode terminals are disposed at both ends of the conductive thin film, and the first pair A high-frequency carrier signal current and a DC bias current are simultaneously applied to the electrode terminals of the first recording medium and reproduced by a magnetic head that reproduces a high-frequency reproduction signal modulated by a recording magnetic field from the second pair of electrode terminals. And a two-layer perpendicular magnetic recording medium using a soft magnetic layer film,
The coercive force value of the soft magnetic layer film is a value close to the coercive force value of a DC magnetic field bias generated by the DC bias current of the magnetic head.
[0017]
According to an eighth aspect of the present invention (corresponding to claim 8), a conductive thin film is sandwiched between soft magnetic materials, two or more pairs of electrode terminals are disposed at both ends of the conductive thin film, and the first pair A high frequency carrier signal is applied to the electrode terminals of the first electrode, a high frequency reproduction signal modulated by the recording magnetic field is reproduced from the second pair of electrode terminals, and a magnetic head that applies a DC magnetic field bias to the soft magnetic material is reproduced. In a two-layer perpendicular magnetic recording medium using a perpendicular recording layer and a soft magnetic layer film,
In the two-layer perpendicular magnetic recording medium, the coercive force value of the soft magnetic layer film is a value close to the coercive force of the DC magnetic field bias from a DC bias applying means formed in a part of the magnetic head. is there.
[0018]
According to a ninth aspect of the present invention (corresponding to claim 9), the coercive force value of the soft magnetic layer film is larger than the disturbance magnetic field, and the two-layer film vertical according to the seventh or eighth aspect of the invention is characterized in that It is a magnetic recording medium.
[0019]
According to a tenth aspect of the present invention (corresponding to claim 10), the soft magnetic layer film is a laminated film composed of a metal magnetic layer film and an insulating layer film. A double-layer perpendicular magnetic recording medium according to any one of the inventions.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.
(Embodiment 1)
First, a first embodiment will be described with reference to the drawings.
[0021]
FIG. 1 is a conceptual diagram of the magnetic recording / reproducing system of the present invention. FIG. 2 is a view of the single pole portion of the MI head constituting a part of the present invention from the direction P in FIG. FIG. 3 shows a BH curve comparing the characteristics of the backing layer of the magnetic recording medium of the present invention with those of the conventional backing layer. In FIG. 1, a double-layered perpendicular magnetic recording medium 1 includes a disk-shaped glass substrate 4, a backing layer 3 mainly composed of a soft magnetic material, and a perpendicular recording layer 2. The magnetic head flies at a fixed distance d from the perpendicular recording layer 2 and reads a signal recorded on the perpendicular recording layer. In this case, although not shown in the figure, this magnetic head is mounted on a slider of a hard disk drive and floats on a rotating hard disk (here, a double-layer perpendicular magnetic recording medium) at a certain distance. .
[0022]
The magnetic head is constructed by sandwiching a copper conductive thin film between single poles 5 which are main poles made of permalloy, and the principle of extracting signals from both ends of the conductive thin film 6 during reproduction is as shown in FIG. It is.
[0023]
In this case, the signal magnetic flux 9 from the signal magnetization 10 on the perpendicular recording layer 2 forms a closed loop through the perpendicular return core 7 and the backing layer 3. The magnetic flux is detected by the MI effect. FIG. 2 shows the single pole 5 seen from the direction P in FIG. This will be described in comparison with FIG. A high-frequency current is applied from the high-frequency transmitter 16 to the pair of terminals 13 and 14 of the conductive thin film formed on the single pole 5 through the resistor 15. Further, an electric circuit is connected to the other pair of terminals 11 and 12 to detect a voltage drop.
[0024]
In the magnetic reproducing method of the present invention, 17 characteristics having a coercive force larger than the magnetic field strength of the disturbance are obtained with respect to the characteristic 18 of the conventional undercoating layer in FIG. Usually, the magnetic field intensity of disturbance is 10 Oe or less. That is, this backing layer was set to be a soft magnetic film having a slight coercive force of 10 Oe.
[0025]
With this setting, for a disturbance magnetic field of 10 Oe or less, the B / H gradient is small, as shown by the point in FIG. It was found that the disturbance magnetic field induced from the medium to the magnetic head hardly occurs. Further, it was found that the output at the terminals 11 and 12 suddenly increased when a direct current was applied from the winding 8 of the magnetic head to generate and increase a direct current magnetic field bias. At this time, as shown by the point (a) in FIG. 3, when the DC magnetic field bias is set in the vicinity of 10 Oe, the gradient of B / H increases, that is, the differential permeability seems to have increased. When a predetermined coercive force is set as the backing layer of the perpendicular magnetic recording medium, the differential magnetic permeability increases in the vicinity of the coercive force, and a region having a high magnetic permeability can be used.
[0026]
Therefore, since the magnetic permeability of the characteristic 18 of the soft magnetic layer of the conventional backing layer in FIG. 3 is large, the influence of the disturbance magnetic field is greatly generated. In the medium of the present invention, in the region where no DC magnetic field bias is applied. Since the magnetic permeability is low, there is no influence of a disturbance magnetic field and the like, and therefore the above-mentioned problems are solved such that noise is not induced from the entire surface of the magnetic disk. On the other hand, in the MI head, a DC magnetic field bias is necessary to use a region for reducing the sensitivity and distortion of the signal. In the present invention, this DC magnetic field bias and the DC magnetic field bias applied to the backing layer of the two-layer magnetic recording medium are used in common. That is, a direct current magnetic field bias is generated by applying a direct current to the winding 8 of the magnetic head. Although this DC magnetic field bias may erase the magnetization recorded in the perpendicular recording layer, if the coercive force of the perpendicular recording layer is made sufficiently large to 1200 Oe, the output is only attenuated within 0.5 dB, and thereafter It was found that there was no problem in practical use without attenuation.
[0027]
Further, the characteristics of the present invention will be described in detail with reference to FIG. FIG. 4 shows a measurement result of a 0.5 μm permalloy film used as a backing layer of the magnetic recording medium of the present invention by a magnetic permeability measuring device. In the magnetic permeability characteristic 17 of 200 MHz, the magnetic permeability is maximum at a DC bias of 10 Oe, the DC bias value of 10 Oe tends to increase slightly at 1 GHz, and the magnetic permeability 18 decreases. Since the carrier signal is high for use in the MI head, characteristics that can be used even at 1 GHz or higher are required. The cause seems to be eddy current.
(Embodiment 2)
Next, a second embodiment will be described with reference to the drawings.
[0028]
The characteristics shown in FIG. 5 are those of a film in which a backing layer is laminated with permalloy and SiO2.
A laminated film having 10 layers of a permalloy film and a SiO2 film of 50 nm was used. It can be seen that the characteristic 19 of 200 MH and the characteristic 20 of 1 GHz almost coincide. By forming the backing layer in this way, the magnetic permeability of the backing layer only in the portion applied from the magnetic head is improved and functions as the original backing layer. In other parts, the magnetic permeability is low and it does not respond to the magnetic field of the disturbance, so that a high-quality signal can be obtained as a whole.
[0029]
The terminals of the present invention are not limited to the two pairs in the above-described embodiment, and a terminal for applying a high frequency signal and a terminal for applying a direct current for generating a DC magnetic field bias are separately provided to detect signals. In short, it is sufficient that the DC magnetic field bias and the high-frequency signal can be applied, such as three terminals in combination with the terminals.
[0030]
Furthermore, the DC magnetic field bias of the present invention is not limited to the one in which the DC current in the above-described embodiment is applied to the winding of the magnetic head to generate the DC magnetic field bias. In short, it is only necessary to be able to generate a DC magnetic field bias, such as one that generates a DC magnetic field bias by applying a DC current to the conductive thin film provided on the substrate.
[0031]
Furthermore, the coercive force of the backing layer of the present invention is not limited to 10 Oe in the above-described embodiment, but may be 20 Oe, 5 Oe, or the like, in other words, it only needs to have a coercive force larger than the disturbance magnetic field.
[0032]
Furthermore, the substrate of the present embodiment is not limited to the glass substrate in the above-described embodiment, and may be a substrate such as a quartz substrate that can form a backing layer and a perpendicular recording layer.
[0033]
【The invention's effect】
As is clear from the above description, the present invention applies a DC bias magnetic field to both the DC bias of the MI head and the double-layer perpendicular magnetic recording medium, and reduces the coercive force of the backing layer of the double-layer perpendicular magnetic recording medium. By setting the MI head near the DC bias level, it is possible to provide a magnetic recording / reproducing system that is resistant to disturbance magnetic fields.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a magnetic recording / reproducing system using an MI head and a double-layered perpendicular magnetic recording medium according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram of the MI element of the magnetic recording / reproducing system of the present invention. FIG. 3 is a characteristic diagram of the backing layer of the magnetic recording medium of the present invention. FIG. 5 is a characteristic diagram of the backing layer of the magnetic recording medium of the present invention according to the second embodiment of the present invention. FIG. 6 is a schematic diagram of a perpendicular magnetic recording system using a film perpendicular magnetic recording medium according to a conventional invention. FIG. 7 is a diagram showing the principle of operation of the MI head according to the conventional invention. FIG. 8 is a diagram showing the principle of operation of the MI head according to the conventional invention.
DESCRIPTION OF SYMBOLS 1 Double layer perpendicular | vertical magnetic recording medium 2 Perpendicular recording layer 3 Backing layer 4 Glass substrate 5 Single pole 6 Conductive thin film 7 Return core 8 Magnetic head winding 9 Signal magnetic flux 10 Signal magnetization 11 Terminal 12 Terminal 13 Terminal 14 Terminal 15 Resistance 16 High-frequency transmitter 17 Characteristics of backing layer of the present invention 18 Characteristics of conventional backing layer 19 200 MHz characteristics 20 1 GHz characteristics 21 Magnetic flux 22 Winding wire 23 Playback terminal 24 Playback terminal 25 Lead 26 Track width 27 Permalloy film 28 SiO2 film 29 Soft magnetism Core 30 Soft magnetic core 31 High frequency oscillator 32 Resistance 33 Current 34 Terminal 35 Terminal 36 Magnetic recording medium 37 Magnetization 38 DC bias 39 200 MHz characteristic 40 1 GHz characteristic 41 DC bias winding

Claims (10)

A conductive thin film is sandwiched between soft magnetic materials, two or more pairs of electrode terminals are arranged on both ends of the conductive thin film, and a high frequency carrier signal current and a DC bias current are simultaneously applied to the first pair of electrode terminals. In a magnetic reproducing method using a magnetic head for reproducing a high frequency reproduction signal modulated by a recording magnetic field from a second pair of electrode terminals,
When a two-layer perpendicular magnetic recording medium using a perpendicular recording layer and a soft magnetic layer film is to be reproduced, a DC magnetic field bias by the DC bias current is set to a value close to the coercive force of the soft magnetic layer film. Magnetic reproduction method. A conductive thin film is sandwiched between soft magnetic materials, two or more pairs of electrode terminals are disposed at both ends of the conductive thin film, a high frequency carrier signal is applied to the first pair of electrode terminals, and the second pair In a magnetic reproducing method by a magnetic head that reproduces a high-frequency reproduction signal modulated by a recording magnetic field from an electrode terminal of the magnetic head and applies a DC magnetic field bias to the soft magnetic material,
When reproducing a dual-layer perpendicular magnetic recording medium using a perpendicular recording layer and a soft magnetic layer film,
A magnetic reproducing method characterized in that the DC magnetic field bias is set to a value close to the coercive force of the soft magnetic layer film by a DC bias applying means formed in a part of the magnetic head. 3. A magnetic reproducing method according to claim 1, wherein a coercive force of the soft magnetic layer film is larger than a disturbance magnetic field. 4. The magnetism according to claim 1, wherein the soft magnetic layer film of the two-layer film perpendicular magnetic recording medium is a laminated film composed of a metal magnetic layer film and an insulating layer film. Playback method. A conductive thin film is sandwiched between soft magnetic materials, two or more pairs of electrode terminals are disposed at both ends of the conductive thin film, and a high frequency carrier signal current and a DC bias current are simultaneously applied to the first pair of electrode terminals. In the magnetic head for reproducing the high frequency reproduction signal modulated by the recording magnetic field from the second pair of electrode terminals,
When a two-layer perpendicular magnetic recording medium using a perpendicular recording layer and a soft magnetic layer film is to be reproduced, the DC magnetic field bias due to the DC bias current is set to a value close to the coercive force of the soft magnetic layer film. Magnetic head characterized by A conductive thin film is sandwiched between soft magnetic materials, two or more pairs of electrode terminals are arranged at both ends of the conductive thin film, a high frequency carrier signal is applied to the first pair of electrode terminals, and the second pair In a magnetic head that reproduces a high-frequency reproduction signal modulated by a recording magnetic field from the electrode terminal of the magnetic terminal and applies a DC magnetic field bias to the soft magnetic body,
When reproducing a double-layer perpendicular magnetic recording medium using a perpendicular recording layer and a soft magnetic layer film,
The magnetic head according to claim 1, wherein the DC magnetic field bias from a DC bias applying means formed in a part of the magnetic head is set to a value near the coercive force of the soft magnetic layer film. A conductive thin film is sandwiched between soft magnetic materials, two or more pairs of electrode terminals are arranged on both ends of the conductive thin film, and a high frequency carrier signal current and a DC bias current are simultaneously applied to the first pair of electrode terminals. And a two-layered perpendicular magnetic recording medium which is reproduced by a magnetic head for reproducing a high-frequency reproduction signal modulated by a recording magnetic field from a second pair of electrode terminals, and which uses a perpendicular recording layer and a soft magnetic layer film In
2. The double-layered perpendicular magnetic recording medium according to claim 1, wherein the coercive force value of the soft magnetic layer film is a value close to the coercive force value of a DC magnetic field bias caused by the DC bias current of the magnetic head. A conductive thin film is sandwiched between soft magnetic materials, two or more pairs of electrode terminals are disposed at both ends of the conductive thin film, a high frequency carrier signal is applied to the first pair of electrode terminals, and the second pair A high-frequency reproduction signal modulated by a recording magnetic field is reproduced from an electrode terminal of the magnetic disk and reproduced by a magnetic head that applies a DC magnetic field bias to the soft magnetic material, using a perpendicular recording layer and a soft magnetic layer film In a two-layered perpendicular magnetic recording medium,
2. The double-layered perpendicular magnetic recording medium according to claim 1, wherein the coercive force value of the soft magnetic layer film is a value close to the coercive force of the DC magnetic field bias from a DC bias applying means formed in a part of the magnetic head. 9. The two-layer perpendicular magnetic recording medium according to claim 7, wherein the coercive force value of the soft magnetic layer film is larger than a disturbance magnetic field. 10. The double-layered perpendicular magnetic recording medium according to claim 7, wherein the soft magnetic layer film is a laminated film composed of a metal magnetic layer film and an insulating layer film.

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