JP2000182217A - Magnetic head and magnetic recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an MI head high in sensitivity by detecting only a signal based upon variation in the resistance component of impedance. SOLUTION: This device is provided with a conductive thin film 11, a soft magnetic body 12 formed sandwiching the conductive thin film 11, a 1st couple of electrode terminals 13 and 14 which are connected to both the ends of the conductive thin film 11, a 2nd couple of electrode terminals 16 and 17 which are connected to both the ends of the conductive thin film 11, an applying circuit 8 which applies a high-frequency carrier signal and a DC current to the electrode terminals 13 and 14 at the same time, and a signal detecting means 23 which detects variation in the resistance component of the impedance of the electrode terminals 16 and 17 due to an electric magnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active magnetic head and a high-density magnetic recording / reproducing apparatus using a highly sensitive impedance change of a high-frequency carrier signal.

[0002]

2. Description of the Related Art FIG. 6 is reported in Technical Report MR95-85 of the Institute of Electronics, Information and Information Engineers and is proposed as an element and a head using a change in magnetic impedance. FIG. 6 shows a detection conductor thin film 45 composed of a conductive metal thin film and a laminated film 49 of a permalloy film 47 and a SiO2 film 48 along a track width 46.
And 50 illustrate the principle of operation of a magneto-impedance element sandwiched by soft magnetic cores. UHF
A high-frequency signal is applied from a high-frequency signal generator 51 of the band via a resistor 52 to pass a current 53, and based on a change in magnetic impedance between terminals 54 and 55 provided at both ends of the detection conductor thin film 45, It detects a voltage change between terminals. When there is no signal magnetic field generated from the magnetization 57 on the magnetic recording medium 56, the current 53 and the terminals 54 and 5 of the detection conductor thin film 45 are connected between the terminals 54 and 55.
When a voltage of a UHF carrier signal corresponding to the product of the impedances of the elements 5 is generated and a signal magnetic field from the magnetic recording medium is received, the easy magnetization direction of the soft magnetic core of the element is oriented in the track width direction. Therefore, the magnetization is inclined from the orientation direction by the signal magnetic field, and the magnetic impedance is reduced. Therefore, the UHF carrier signal is detected in a form where it is AM-modulated by the signal magnetic field of the magnetic recording medium. The signal magnetization 57 on the magnetic recording medium 56 can be read by AM detection of this signal. If this head is realized, it is expected that there is a possibility that an output about 10 times higher than that of a giant MR head currently under development may be obtained. FIG. 7 shows FIG.
The operation curve of the element shown in FIG. That is,
The high frequency voltage detected at the terminals 54 and 55 is plotted. A high frequency voltage detected at terminals 54 and 55 is obtained by applying a dc magnetic field to the above element at the center of a 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 54 and 55 is the largest. As the DC magnetic field increases, the high-frequency voltage detected at the terminals 54 and 55 decreases. This DC magnetic field corresponds to the signal magnetic field on the magnetic recording medium 56. As can be seen from FIG. 7, it is necessary to set DC bias 58 points in order to reproduce a signal with high sensitivity and obtain a waveform with small distortion. In the above model, a carrier signal and a DC current are caused to flow through a conductor to generate a DC magnetic field, which is used as a bias. However, the operating characteristics at high frequencies are not clear, and a new method for detecting impedance changes at high frequencies is necessary to obtain high-sensitivity impedance changes along with this analysis.

[0003]

As described above, the realization of a high-sensitivity magnetic head for realizing high-density recording is desired. However, the operating characteristics of the impedance at high frequencies are not clear. There is a problem that it is necessary to find a suitable detection method.

An object of the present invention is to realize a highly sensitive magnetic head by devising a novel detection method and detecting only a signal due to a change in impedance resistance.

[0005]

In order to solve the above-mentioned problems, a first invention (corresponding to claim 1) comprises a conductive thin film and a soft magnetic material formed so as to sandwich the conductive thin film. A first pair of electrode terminals connected to both ends of the conductive thin film; a second pair of electrode terminals connected to both ends of the conductive thin film; A magnetic head comprising: an application circuit for simultaneously applying a carrier signal and a direct current; and signal detection means for detecting a change in a resistance component of impedance at the second pair of electrode terminals due to an external magnetic field. .

A second invention (corresponding to claim 2) is:
The signal detection means is a phase detector connected to the second pair of electrode terminals, and has a reference signal as:
The magnetic head according to the first invention, wherein the high-frequency carrier signal current is used.

A third aspect of the present invention (corresponding to claim 3) is:
The magnetic head according to the second invention, wherein the phase detector uses, as a reference signal, a high-frequency carrier signal whose phase direction is set so that the level of the detected high-frequency signal is maximized.

A fourth invention (corresponding to claim 4) is:
A magnetic head according to any one of the first to third inventions, a recording medium holding means for holding a recording medium for reproducing a signal recorded by the magnetic head, and a designated position on the recording medium. A magnetic recording / reproducing apparatus comprising: a positioning unit for positioning a magnetic head.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS.

First, as an experiment, a width of 300 μm and a length of 3 m
The head shown in FIG. 6 having a gap of 0.3 μm, a length of the detection conductor thin film made of copper (cu): 2 mm, a width of the detection conductor thin film: 400 μm, and a thickness: 1 μm is manufactured by using a soft magnetic material of FeTaN m and Analysis was performed on the impedance at both ends. At that time, instead of the signal magnetic field from the magnetic recording medium, a DC magnetic field was applied in the length direction of the magnetic material by a Helmholtz coil as an external magnetic field. When the DC magnetic field is 5 Oe, the magnetic material used in this experiment is completely saturated. FIGS. 1 and 2 show the results of analyzing the change in impedance. FIG. 1 shows the change of the total impedance of the MI element measured by the impedance meter. The characteristic 1 when the external magnetic field is zero is the characteristic 2 when the external magnetic field 5 Oe is applied and the characteristic 2 when the external magnetic field is 5 Oe as indicated by an arrow 3 indicating the change. Changes to The larger the difference is, the higher the impedance change rate is, and a larger output can be obtained. Further, the impedance meter can measure the inductance component and the resistance component separately. These are called an inductance component and a resistance component, respectively. FIG. 2 shows the imaginary part, in this case, the characteristic of the inductance component and the characteristic of the resistance component to an external magnetic field. As in the case of FIG. 1, when the external magnetic field of FIG. 2 is 5 Oe, the magnetic material used in this experiment is completely saturated. As can be seen from FIG. 1, at low frequencies, the impedance changes with respect to the external magnetic field (DC magnetic field), but at high frequencies (1 G
Hz), this analysis revealed that there was almost no change. However, since the impedance change rate of the MI effect is proportional to the product of the frequency and the change rate of the magnetic permeability of the magnetic material, it is known that it is important to operate in a high-frequency region in order to increase this. As a cause of this analysis, the characteristic in FIG. 1 shows a characteristic similar to the change in the inductance component shown in FIG. 2, and the inductance that does not change due to the external magnetic field is limited in the high frequency region by the inductance of the lead and the like. On the other hand, the analysis revealed for the first time that the resistance component shown in FIG. 2 changed significantly with respect to the external magnetic field. More specifically, the characteristic 4 of the inductance component when the external magnetic field is zero in FIG. 2 is the sum of the inductance generated from the real part of the magnetic permeability and the inductance of the detection conductor. The characteristic of the inductance component at 5 Oe becomes 5, and the magnetic permeability approaches the value of 1 in air, so that mainly the inductance component of only the detection conductor remains. The characteristic 6 of the resistance component when the external magnetic field is zero is the sum of the resistance component generated from the imaginary part of the magnetic permeability of the magnetic body and the resistance component of the detection conductor. Since the magnetic permeability of the imaginary part is 1, as shown by the characteristic 7 of the resistance component, the resistance component of the detection conductor which does not change due to the external magnetic field is mainly used. The present invention has been devised based on the findings of these analyses. In other words, it has been found that it is important to subtract an inductance component that does not change due to an external magnetic field and detect a signal based only on a resistance component that changes according to the external magnetic field.

(Embodiment 1) FIG. 3 is a block diagram showing the configuration of Embodiment 1 of the present invention. FIG. 4 shows the operation principle of the phase detector. FIG.
Shows an MI head of the present invention formed on a head slider by using photolithography technology.

From a high frequency signal generator 8 via a resistor 9
A high frequency carrier signal is supplied to the MI head 10. MI
The head 10 is made of a detection conductor thin film 11 made of Cu and made of FeTa.
It is formed so as to be sandwiched by N amorphous soft magnetic bodies 12. Further, the detection conductor thin film 12 was integrally formed with two pairs of electrode terminals, that is, an electrode terminal 13 for supplying a high-frequency carrier, a ground electrode terminal 14, and a detection electrode terminal 16 and a ground electrode terminal 17. In addition, the ground electrode terminal 14
And 17 are connected to grounds 18 and 19. This grounding does not necessarily have to be divided into two places, but is effective at one place depending on the structure of the head. Next, the detection electrode terminal 16
Is transmitted to the phase detector 23 via the amplifier 20. On the other hand, a high-frequency carrier signal from the high-frequency signal generator 8 is used as a reference signal by the resistor 21 and the amplifier 2.
2 to the phase detector 23 via
A signal generated by a change in the resistance component of the impedance of the head 10 can be selectively detected. The signal is obtained at terminal 24 as an output. Further, the operation principle of the phase detector will be described with reference to FIG. The output 41 generated by the change in the total impedance at the electrode terminal 16 of the detection conductor described above rotates counterclockwise on the circle shown in FIG. 4 at the frequency of the high-frequency carrier signal, and the amplitude is also AM.
Modulated and changing. On the other hand, when the high-frequency carrier signal is used as the reference signal of the phase detector via the resistor 21, the output of the reference signal in the vector 44 direction in the X direction shown in FIG. 4 is detected. An output 43 of the output signal 41 in the X direction is detected, that is, a signal generated by a change in the resistance component (R component). Also, the output signal 42 generated by the inductance component (L component) when the phase θ is 90 degrees (Y direction) has an output at the terminal 24 because the component in the reference signal direction is zero. Next, the signal thus obtained is applied to an AM detector to demodulate the signal of the magnetic recording medium.
In this experiment, since the lead to the magnetic head was long and the inductance component was large, the present invention was extremely effective for obtaining a large rate of change in impedance. In addition,
In the present invention, the direction of the resistance component is designated as the reference signal. However, when the lead is shortened and the inductance component is reduced, the impedance change of both the L component and the R component can be used. It is also effective to select and use the above phase direction. Therefore, the detection signal can be maximized by optimizing the phase direction of the reference signal by the L component and the R component of the configured head impedance. One example is the L component and R of the head impedance.
The high-frequency signal applied to the component becomes a signal having a phase determined by L and R, and it is also useful to use this signal as a reference signal. MI configured as above
When an external magnetic field 15 from a magnetic recording medium is applied to the head in the direction of the arrow, a high-frequency carrier signal is generated at the detection electrode terminal 16 as an AM-modulated signal.

FIG. 5 is a perspective view of a prototype head slider. As is clear from FIG. 4, the MI head 10 was formed on the protrusion 25 of the head slider. HD
In D, the lower surface of the head slider (the lower surface in the figure) floats at a fixed interval from the magnetic recording medium to reproduce a signal. The MI head 10 receives 15 signal magnetic fields (external magnetic fields) from the magnetic recording medium. The circuit block 26 contains a high-frequency signal generator and an AM detector,
From the signal supply terminal 27 from the high frequency signal generator to the conductor film 2
8, the high-frequency carrier supply terminal 2 on the head forming surface
It is conveyed to 9. Similarly, a ground terminal 30, a ground conductor film 31, and a ground terminal 32 were formed. These conductor films and terminals were formed on a substrate 33 made of ceramics by photolithography. Reference numeral 34 denotes an amplifier and a phase detector, and outputs are a terminal 35, a conductor film 36, a terminal 3
7, grounding terminal 38, conductive film 39, grounding terminal 40
Conveyed by Thereafter, the output is transmitted from the terminal 37 to the AM detector and becomes a reproduced signal.

The display of the power supply system of the amplifier is omitted because the drawing becomes complicated. By providing the amplifier and the phase detector on the head slider as described above, the inductance and the resistance can be reduced by shortening the length of the detection conductor, so that a head having a large change rate can be obtained.

Although the FeTaN amorphous material is used as the soft magnetic material described in the embodiment of the present invention, other soft magnetic materials such as Co-based, Fe-based amorphous magnetic material, permalloy, and sendust are also effective. It is.
Further, although Cu is used as the detection conductor, it is needless to say that a conductive material such as Ag, Au, or Al is also effective.

The high-frequency signal generator and the resistor according to the present embodiment are examples of the application circuit according to the present invention.

[0017]

As is apparent from the above description, the present invention can provide a high-sensitivity magnetic head by detecting only a signal due to a change in the impedance resistance component.

[Brief description of the drawings]

FIG. 1 is an impedance characteristic diagram on which the present invention is based.

FIG. 2 is a characteristic diagram showing an analysis result of impedance characteristics on which the present invention is based;

FIG. 3 is a block diagram of a configuration according to the first embodiment of the present invention;

FIG. 4 is an operation principle diagram of the phase detector according to the first embodiment of the present invention;

FIG. 5 is a configuration diagram of an MI head according to the first embodiment of the present invention.

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

FIG. 7 is a diagram illustrating the operation principle of a conventional MI head.

[Explanation of symbols]

 1 Characteristics at zero external magnetic field 2 Characteristics at external magnetic field 5 Oe 3 Arrows indicating changes 4 Characteristics of inductance component at zero external magnetic field 5 Characteristics of inductance component at external magnetic field 5 Oe 6 Characteristics of resistance component at zero external magnetic field 7 Characteristics of resistance component when external magnetic field is 5 Oe 8 High frequency signal generator 9 Resistance 10 MI head 11 Detection conductor thin film 12 Soft magnetic material 13 Electrode terminal 14 Electrode terminal 15 External magnetic field 16 Electrode terminal 17 Electrode terminal 18 Ground 19 Ground 20 Amplifier 21 Resistance Reference Signs List 22 amplifier 23 phase detector 24 output terminal 25 convex part of head slider 26 circuit block 27 signal supply terminal 28 conductor film 29 high-frequency carrier supply terminal 30 grounding terminal 31 conductor film 32 grounding terminal 33 substrate 34 amplifier and phase detector 35 Terminal 36 Conductor film 37 Terminal 38 Grounding terminal 39 Conductor Film 40 Grounding terminal 41 Output signal 42 Output signal 43 Output 44 Vector 45 Detection conductor thin film 46 Track width 47 Permalloy film 48 SiO2 film 49 Soft magnetic core 50 Soft magnetic core 51 High frequency signal generator 52 Resistance 53 Current 54 Terminal 55 Terminal 56 Magnetic recording medium 57 Magnetization 58 DC bias

Claims (4)

[Claims] 1. A conductive thin film, a soft magnetic material formed so as to sandwich the conductive thin film, a first pair of electrode terminals connected to both ends of the conductive thin film, and both ends of the conductive thin film A second pair of electrode terminals connected to the first pair of electrode terminals; an application circuit for simultaneously applying a high-frequency carrier signal and a direct current to the first pair of electrode terminals; and a resistance component of impedance at the second pair of electrode terminals. A magnetic head comprising: signal detection means for detecting a change due to an external magnetic field. 2. The signal detector according to claim 1, wherein the signal detector is a phase detector connected to the second pair of electrode terminals, and uses the high-frequency carrier signal current as a reference signal. The magnetic head as described. 3. The magnetic head according to claim 2, wherein the phase detector uses a high-frequency carrier signal whose phase direction is set so that the level of the detected high-frequency signal is maximized, as a reference signal. . 4. A magnetic head according to claim 1, a recording medium holding means for holding a recording medium for reproducing a signal recorded by the magnetic head, and a designation on the recording medium. And a positioning means for positioning the magnetic head at a set position.