JP2002216311A - Magnetic head and magnetic reproducing machine which uses this head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic head that can detect only the impedance components changing by the magnetic field of a signal while canceling the impedance components which do not change. SOLUTION: A first and second conductive magnetic film layers and a pair of soft magnetic shields to form the first and second film layers vertical to the magnetic recording medium are provides together with a magnetic field applying means to apply a dc magnetic field to those film layers and a common terminal connected to one side of the first and third electrodes out of the first to forth electrodes formed on both sides of the first and second magnetic film layers, the first and second electrode terminals formed on both sides of the second electrode at the other side, and the third and forth electrode terminals formed on both sides of the forth electrode. A high frequency generator is connected to the first and third electrode terminals, and a differential amplifier is also connected to the second and forth electrode terminals and to the common terminal to detect the impedance of the first conductive magnetic film layer changing by the magnetic field of the signal as the high frequency carrier signal change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel high-sensitivity active magnetic head using a new high-frequency impedance change and a high-density magnetic reproducing apparatus using the same.

[0002]

2. Description of the Related Art FIG. 5 is an IEICE technical report MR95-8.
FIG. 1 is an operation principle diagram of a conventional magnetic reproducing apparatus disclosed in No. 0, and is proposed as an element and a head using a change in magnetic impedance. In the impedance element shown in FIG. 5, the detection conductor film 28 made of a conductive metal thin film has a permalloy film 3 over a track width 29.
The structure is sandwiched between soft magnetic cores 32 and 33 each composed of a laminated film of an O ₂ and an SiO ₂ film 31.

In FIG. 5, first, a high frequency transmitter 3 in the UHF band is used.
The current 36 is applied by applying a high-frequency signal transmitted from the detection conductor thin film 4 through a resistor 35, and based on a change in magnetic impedance generated between terminals 37 and 38 provided at both ends of the detection conductor thin film 28, the terminal is detected. Detects a voltage change between them.

When there is no signal magnetic field generated from the magnetization 40 on the magnetic recording medium 39, the product of the current 36 and the impedance between the terminals 37 and 38 in the detection conductor thin film 28 is applied between the terminals 37 and 38. A UHF carrier signal having a voltage corresponding to. On the other hand, when receiving a signal magnetic field from the magnetic recording medium 39, the easy magnetization direction of the soft magnetic cores 32 and 33 in the impedance element is oriented in the track width direction.
Since the direction of magnetization changes due to the signal magnetic field,
The magnetic impedance is reduced by the slope.
According to such a principle, the UHF carrier signal is detected in the form of AM modulation depending on the presence or absence of the signal magnetic field of the magnetic recording medium 39. That is, the signal magnetization 40 on the magnetic recording medium 39 can be read by AM detection of such a signal.

By realizing a magnetic head having such a configuration, it is expected that an output about ten times higher than that of a giant MR head currently under development in various fields can be obtained. FIG. 6 shows an operation curve of the conventional impedance element shown in FIG. 5. Under the condition that the carrier signal frequency is 1.0 GHz, a DC magnetic field is applied to the impedance element at the center of the Helmholtz coil. It is obtained by adding.

As is apparent from FIG. 6, in order to reproduce a signal with high sensitivity and obtain a waveform with small distortion, it is necessary to set a DC bias point 41. In the model shown in FIG. 6, a DC magnetic field is generated by flowing a carrier signal and a DC current through a conductor, and the generated DC magnetic field intensity is used as a DC bias point 41.

[0007]

However, in the above-described method, when the size of the detection conductor, particularly the cross-sectional area, is reduced, the resistance value is significantly increased. When the thickness of the magnetic material around the detection conductor is reduced, inductance, That is, there is a problem that the impedance is reduced. Therefore, it becomes difficult to detect a change in impedance, and it is not possible to desire a magnetic head with high sensitivity.

In order to improve the linear recording density,
It is desired that the detection unit can be applied to a shielded magnetic head that can detect a signal magnetic field from a strong magnetic recording medium, which is close to the magnetic recording medium, but it is difficult to detect only an impedance change at a high frequency. At the same time, there are many problems such as the necessity of clarifying the operation characteristics of the magnetic head itself.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a high-sensitivity high-frequency impedance type magnetic head by efficiently detecting only a change in impedance.

[0010]

In order to achieve the above object, a magnetic head according to the present invention comprises a first magnetic head in a direction perpendicular to a surface facing a magnetic recording medium, the first magnetic head being arranged from a side facing the magnetic recording medium first. The first conductive magnetic film and the second conductive magnetic film are disposed between the gaps formed by the shield cores,
The distance between the first conductive magnetic film and the second conductive magnetic film is the first.
Are arranged so that the signal magnetic field from the magnetic recording medium is applied only to the conductive magnetic film.

With this configuration, the impedance component that does not change due to the signal magnetic field can be canceled out, and only the impedance component that changes according to the signal magnetic field can be extracted, so that a highly sensitive magnetic head can be provided. Becomes

Further, the magnetic head according to the present invention has the following features.
A pair of soft magnetic bodies for shielding formed by sandwiching the conductive magnetic film and the second conductive magnetic film with an insulator film interposed therebetween; a first conductive magnetic film and a second conductive magnetic film; A means for applying a DC magnetic field to the film, a first electrode and a second electrode formed at both ends of the first conductive magnetic film, a third electrode formed at both ends of the second conductive magnetic film, and Of the fourth electrodes, a first electrode and a third electrode which are arranged on one side with respect to the track.
, A first electrode terminal and a second electrode terminal provided at a second electrode end disposed on the other side of the track, and a third terminal provided at a fourth electrode end. And a high-frequency oscillator connected to the first electrode terminal and the third electrode terminal, and connected to the second electrode terminal, the fourth electrode terminal, and the common terminal. It is preferable to have a differential amplifier and detect the impedance of the first conductive magnetic film, which changes due to the signal magnetic field of the magnetic recording medium, as a change in the high-frequency carrier signal. This is because a relatively large impedance component due to the signal magnetic field can be canceled, so that only a minute impedance change component can be detected.

Further, in the magnetic head according to the present invention, it is preferable that the effective magnetic permeability of the shield core at a high frequency carrier signal frequency is smaller than the effective magnetic permeability of the first conductive magnetic film and the second conductive magnetic film. This is because the conductive magnetic film can respond to the high-frequency carrier signal.

Further, the magnetic head according to the present invention has the following features.
It is preferable that the thicknesses of the conductive magnetic film and the second conductive magnetic film are not more than the skin depth at the high frequency carrier signal frequency. This is because it is possible to avoid dimensional restrictions for incorporating the magnetic head.

Also, the magnetic head according to the present invention has the following features.
A shield core sandwiching the first conductive magnetic film and the second conductive magnetic film, a first magnetic body having excellent high-frequency characteristics on a surface facing the first conductive magnetic film and the second conductive magnetic film; And a second magnetic body responsive to a signal generated from the magnetic recording medium. This is because the impedance per magnetic flux can be further increased, so that a magnetic head with higher sensitivity can be provided.

In the magnetic head according to the present invention, it is preferable that a DC bias is applied to the first conductive magnetic film and the second conductive magnetic film by superimposing a DC current on a high-frequency carrier signal current. . This is because, by simultaneously applying the high-frequency carrier signal current, both the external impedance and the internal impedance are changed, and the resistance change due to the external impedance is canceled.

According to another aspect of the present invention, there is provided a magnetic reproducing apparatus comprising: a magnetic head as described above;
A recording medium holding means for reproducing a signal recorded by the magnetic head and a positioning means for positioning the magnetic head to a designated position on the recording medium are provided.

With this configuration, the impedance component that does not change due to the signal magnetic field can be cancelled, and only the impedance component that changes according to the signal magnetic field can be extracted. Therefore, a magnetic reproducing apparatus having a highly sensitive magnetic head can be provided. Can be provided.

[0019]

Embodiment 1 Hereinafter, a magnetic head according to Embodiment 1 of the present invention will be described with reference to the drawings.

First, the principle of the present invention will be described. It is self-evident electromagnetically that the inductance is determined by the number of intersections between the magnetic flux generated at this time and the current flowing through the conductor. Here, the inductance determined by the current inside the conductor and the magnetic flux generated inside the conductor is defined as the internal inductance, and the inductance determined by the current flowing inside the conductor and the magnetic flux generated outside the conductor is defined as the external inductance.

Therefore, for example, the inductance when a non-magnetic conductor wire is wound around a magnetic material and the inductance when a soft magnetic material is formed around a non-magnetic conductor can be considered as external inductance.

Conventional methods for detecting signals in a magnetic head include the aforementioned MR (Magneto-Resistivity) and G
A method using resistance change such as MR (Giant Magneto-Resistivity), a method using eddy current such as MI effect to detect a signal by a resistance change due to skin depth changing by a magnetic field, and a method shown in the conventional example. Soft magnetic material and S
There is a method in which a conductive metal film is sandwiched between films in which an iO ₂ film is laminated, and detection is performed using an impedance that changes by applying a signal magnetic field using an external impedance.

The signal detecting method in the magnetic head according to the embodiment of the present invention mainly detects a change due to a signal magnetic field in the internal inductance of the ribbon-shaped conductive magnetic thin film as the first magnetic material. In addition to this, a second magnetic film is formed on the surface of the shield core to combine external impedances, and a change in the internal and external impedances due to a magnetic field is used as a signal detection method.

In general, it is well known that the resistance component of a conductive metal film increases in inverse proportion to its cross-sectional area (thickness × width). MI that directly energizes soft magnetic material
When the effect is used, skin depth due to eddy current is generated and the magnitude of the skin depth is used. Therefore,
The film thickness must be dimensionally much larger than the skin depth, which imposes dimensional restrictions for incorporation into a magnetic head. Even in the case of a conventional example in which a soft magnetic material film is formed around a conductive metal film to utilize external impedance, it is related to the cross-sectional area of a conductive film penetrating a magnetic circuit. Since the resistance component that does not change due to the magnetic field becomes extremely large, it is obvious that the change in impedance due to the signal magnetic field is largely masked and it is difficult to detect.

Therefore, the large resistance component is canceled out,
By detecting only the resistance change, a smaller resistance change can be detected.
By arranging two conductive magnetic films between the shield cores of the shield type magnetic head and arranging the differential amplifier, the resistance component which greatly increases due to the thinning of the soft magnetic film is canceled out, and the signal magnetic field is reduced. It is intended to detect only the impedance component that changes due to

In the shield type magnetic head according to the present embodiment, since the thickness of the conductive magnetic film to be inserted into a narrow gap of, for example, 0.1 μm or less needs to be 50 nm or less, it is extremely thin. Become a film,
The resistance component that does not change greatly increases.

Further, detection is performed using the above-described internal inductance, that is, a high-frequency current is applied directly to a thin film having a thickness that does not allow skin depth to occur due to eddy current, and the internal inductance is changed by an applied magnetic field. A magnetic head that detects a signal using a change has not been found so far.

Although the magnetic head according to the present invention is structurally shown to have a structure similar to an MR head or a GMR head, these heads pass a direct current. The magnetic head according to the present invention is different from the magnetic head according to the present invention in that a high-frequency carrier signal is simultaneously superimposed. Therefore, even if a high-frequency current is applied to the conductor thin film of the conventional MR head or GMR head, no output can be obtained unless technical characteristics of the shielding soft magnetic material itself are devised.

FIG. 1 is a sectional view of a magnetic head according to a first embodiment of the present invention, and FIG. 2 is a sectional view of the first embodiment of the present invention.
1 is a plan view of the magnetic head according to FIG. As shown in FIG. 1, the configuration of the magnetic head according to the first embodiment is substantially the same as the configuration of the MR head or the GMR head. However, in the first embodiment, the first conductive magnetic film 1 and the second conductive magnetic film 2 are made of CoNbZr and SiO _2.
And between the shield cores 3 and 4 made of the CoNbZr soft magnetic film and between the insulator gaps 18 made of SiO ₂ . The DC bias and the high-frequency carrier signal current are applied through the resistor 10 by superimposing the DC current from the DC power supply 19 and the high-frequency carrier signal current from the high-frequency transmitter 9.

FIG. 2 is a plan view of the two conductive magnetic films as viewed from the arrow 17 in FIG. When the magnetic head having such a configuration is run in opposition to the magnetic recording medium 6, the magnetic flux from the signal magnetization 5 on the magnetic recording medium 6 passes through the first conductive magnetic film 1 and the shield core 3.
7 and 8 passing through the shield core 4. In this case, the distance w between the first conductive magnetic film 1 and the second conductive magnetic film 2 is made sufficiently large, so that the magnetic recording medium 6
The magnetic fluxes 7 and 8 can be designed so as not to pass through the second conductive magnetic film 2.

On the other hand, FIG. 2 also shows the connection between the first conductive magnetic film 1, the second conductive magnetic film 2, and the differential amplifier 15 described above. In FIG. 2, 20 and 2
Reference numeral 2 denotes an electrode of the first conductive magnetic film 1, and reference numerals 21 and 23 denote electrodes of the second conductive magnetic film 2. A common terminal is formed by connecting the electrodes 20 and 21 on one side of the shield core. 16.

Then, the high-frequency oscillator 9 and the DC power supply 19 are connected, and the high-frequency carrier signal current and the DC bias current are superimposed on the electrode terminals 11 and 12 of the electrodes 22 and 23 via the resistor 10 so as to conduct electricity. The electrode 22
The electrode terminals 13 and 14 in the differential amplifier 1
Connect to 5. Further, the common terminal 16 is connected to the differential amplifier 15
, The resistance components of the first conductive magnetic film 1 and the second conductive magnetic film 2 can be offset, and the signal components can be relatively amplified.

The electrodes 20, 21, 22, and 23 are made of a material film having good conductivity, such as Cu, Al, Au, or Ag, and by forming the film as thick as possible, the first Conductive magnetic film 1 and second conductive magnetic film 2
It is effective to reduce the resistance value.

FIG. 3 shows the frequency characteristics of the effective magnetic permeability of the materials of the first conductive magnetic film 1, the second conductive magnetic film 2, and the shield core. That is, when the high-frequency carrier signal frequency is 1 GHz, the effective magnetic permeability μ1 of the first conductive magnetic film 1 and the second conductive magnetic film 2 is larger than the effective magnetic permeability μc of the shield core. Is preferred. In this way, the conductive magnetic film responds to the region that responds to the high-frequency carrier signal, and the shield core responds to the region that responds to the signal component from the magnetic recording medium. Because you can. Therefore, it is possible to more clearly detect a signal component from the magnetic recording medium.

Although the FeTaN film is used as the first conductive magnetic film 1 and the second conductive magnetic film 2, the present invention is not limited to this.
It goes without saying that any soft magnetic material having conductivity, such as a magnetic material or a FeN material, may be used.

(Embodiment 2) FIG. 4 is a sectional view of a shield type magnetic head according to Embodiment 2 of the present invention. The operation principle of the magnetic head according to the second embodiment is the same as that of the magnetic head according to the first embodiment, and thus detailed description is omitted. The difference between the magnetic head according to the second embodiment and the magnetic head according to the first embodiment is that the conductive magnetic film 26 having a magnetic permeability responding to the carrier signal frequency is provided on the gap surface side of the shield cores 24 and 25. And 27 are formed.

By forming in this way, the signal magnetic flux generated from the magnetic recording medium 6 can be applied to the conductive magnetic films 26 and 2.
7, there is an effect that an external impedance is generated and the impedance per magnetic flux can be increased. As the impedance increases, the voltage that changes due to the signal magnetic field increases, so that a magnetic head with higher sensitivity can be configured.

Although the second embodiment uses FeTaN as the conductive magnetic film similarly to the first embodiment, the present invention is not limited to this.
Any soft magnetic material such as e, FeCo, and FeN may be used.

Further, in the first and second embodiments, the FeTaN film is used as the conductive magnetic thin film, but it is considered that a magnetic material having a small specific resistance such as permalloy is more effective. For example, the specific resistance of the FeTaN film is 75 μm.
Ω-cm, the specific resistance of the permalloy film is 20 μΩ-
cm, the thickness of the conductive magnetic film is 50 nm, the length is 0.5 μm, and the width is 0.5 μm, the thickness can be reduced from about 15 ohms to about 4 ohms. Therefore, in this case, if the resistance value that cancels out is significantly large with respect to the impedance that changes due to the magnetic field, the error that cancels out increases. Therefore, it is effective to select a material having a small specific resistance.

Although SiO ₂ is used as the dielectric forming the gap, the same effect can be expected if an inorganic dielectric film such as alumina or glass is used. Further, a laminated film of a CoZrNb metal magnetic material and SiO ₂ is used as a soft magnetic film for shielding so as not to generate an eddy current. However, the present invention is not particularly limited thereto. Fe-based and Co-based metal magnetic materials, ferrite oxides and the like may be used.

[0041]

As described above, according to the magnetic head of the present invention, two conductive magnetic films are arranged between the gaps of the shield type head and connected to the differential amplifier, so that the signal magnetic field can be improved. Thus, it is possible to provide a magnetic head that cancels out the impedance component that does not change due to the magnetic field and detects only the impedance component that changes according to the signal magnetic field.

[Brief description of the drawings]

FIG. 1 is a sectional view of a magnetic head according to a first embodiment of the present invention;

FIG. 2 is a plan view of the magnetic head according to the first embodiment of the present invention;

FIG. 3 is a magnetic permeability characteristic diagram of a magnetic material used in the present invention.

FIG. 4 is a sectional view of a magnetic head according to a second embodiment of the present invention;

FIG. 5 is an operation principle diagram of a conventional MI head.

FIG. 6 is a diagram illustrating the operation principle of a conventional MI head.

[Explanation of symbols]

Reference Signs List 1 first conductive magnetic thin film 2 second conductive magnetic thin film 3, 4, 24, 25 shield core 5, 40 signal magnetization 6, 39 magnetic recording medium 7, 8 magnetic flux 9 high-frequency signal generator 10, 35 resistance 11 , 12, 13, 14, 20, 21, 22, 23 Electrode terminal 15 Differential amplifier 16 Common terminal 17 Arrow 18 Gap 19 DC power supply 26, 27 Conductive magnetic film 28 Detection conductor film 29 Track width 30 Permalloy film 31 SiO ₂ Film 32, 33 Soft magnetic core 34 High frequency oscillator 36 Current 37, 38 Terminal 41 DC bias

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akio Murata 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5D111 AA12 AA28 BB12 BB16 KK01 KK02

Claims (7)

[Claims] 1. A first conductive magnetic film and a second conductive magnetic film are formed by a shield core in a direction perpendicular to a surface facing a magnetic recording medium, in order from a side facing the magnetic recording medium first. The gap between the first conductive magnetic film and the second conductive magnetic film is arranged between the gaps to be formed, and the signal magnetic field from the magnetic recording medium is applied only to the first conductive magnetic film. A magnetic head characterized by being arranged so as to be widened so as to be applied. 2. A pair of shielding soft magnetic materials formed so as to sandwich the first conductive magnetic film and the second conductive magnetic film with an insulator film interposed therebetween, and Means for applying a DC magnetic field to the conductive magnetic film and the second conductive magnetic film; a first electrode and a second electrode formed at both ends of the first conductive magnetic film; A common terminal connecting the first electrode and the third electrode arranged on one side with respect to the track, of the third electrode and the fourth electrode formed at both ends of the magnetic magnetic film; A first electrode terminal and a second electrode terminal provided at the second electrode end disposed on the other side, respectively;
A high-frequency oscillator having a third electrode terminal and a fourth electrode terminal provided at the fourth electrode end and connected to the first electrode terminal and the third electrode terminal; A differential amplifier connected to the electrode terminal, the fourth electrode terminal, and the common terminal, wherein the impedance of the first conductive magnetic film, which varies with a signal magnetic field of the magnetic recording medium, changes in a high-frequency carrier signal. The magnetic head according to claim 1, wherein the magnetic head is detected as: 3. The magnetic head according to claim 1, wherein the effective magnetic permeability of the shield core at a high-frequency carrier signal frequency is smaller than the effective magnetic permeability of the first conductive magnetic film and the second conductive magnetic film. 4. The magnetic head according to claim 1, wherein the thicknesses of the first conductive magnetic film and the second conductive magnetic film are not more than skin depth at a high frequency carrier signal frequency. 5. The shield core sandwiching the first conductive magnetic film and the second conductive magnetic film is opposed to the first conductive magnetic film and the second conductive magnetic film. 2. The magnetic head according to claim 1, wherein the magnetic head comprises a first magnetic body having a high frequency characteristic and a second magnetic body responsive to a signal generated from the magnetic recording medium. 6. The magnetic head according to claim 1, wherein a direct current is superimposed on a high frequency carrier signal current and applied to the first conductive magnetic film and the second conductive magnetic film as a direct current bias. 7. A magnetic head according to claim 1, a recording medium holding means for reproducing a signal recorded by said magnetic head, and a designated position on said recording medium. A magnetic reproducing apparatus comprising: a positioning unit for positioning a magnetic head.