JPH061524B2 - Magnetic reproducing device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an apparatus for reproducing a signal recorded on a magnetic recording medium, and in particular, reproducing by detecting a recording signal magnetic field from the magnetic recording medium with a magnetic material. The present invention relates to a magnetic reproducing device.

[Technical background of the invention and its problems]

At present, the reproducing method generally adopted in the magnetic recording / reproducing apparatus is a magnetic flux detecting method using a ring type magnetic head. In this method, the reproduction output depends on the magnetic flux, and therefore decreases as the track width decreases. Therefore, there is a limit to the reproduction of the high density recording signal due to the narrow track.

Therefore, the inventors of the present invention, as a magnetic reproducing apparatus based on a magnetic field detection method suitable for reproducing such a high-density recording signal, change the recording signal magnetic field from the magnetic recording medium to a change in the high frequency magnetic characteristics of the magnetic material, for example, high frequency permeability. Also, a method of reproducing by detecting as a change in at least one of the loss terms has been already proposed in Japanese Patent Application Laid-Open No. 57-36407. More specifically, ferrite, Fe
-A magnetic material such as Ni alloy or amorphous alloy is used, and a high frequency circuit is coupled thereto. This high-frequency circuit has a high-frequency coil made of, for example, a thin film conductor, supplies a high-frequency signal to this coil to generate a high-frequency magnetic field, and applies it to a magnetic material. Then, a high frequency signal associated with a change in the high frequency magnetic characteristics of the magnetic material is taken out from the high frequency circuit, and a change in the output of the high frequency signal is detected to obtain a reproduction output.
In this system, since the reproduction output depends on the recording signal magnetic field from the magnetic recording medium and not on the magnetic flux, a large reproduction output can be obtained even when the track width is very narrow, and it is extremely useful for reproducing high density recording signals. It is useful.

By the way, in this method, it is necessary to apply an appropriate static bias magnetic field to the magnetic material in order to obtain a reproduction output with a high level and a good S / N and a low distortion rate. As a conventional bias magnetic field applying means, it is considered that a permanent magnet is incorporated in a reproducing head, or a permanent magnet is arranged on the opposite side of the reproducing head with a magnetic recording medium sandwiched between them. However, according to the former, the structure of the reproducing head and the manufacturing process are complicated, resulting in high cost. Further, the latter structure, in which a permanent magnet is arranged on the opposite side of the magnetic recording medium from the reproducing head, is not suitable for practical use because it has a large arrangement restriction when applied to an actual recording / reproducing apparatus. further,
When a permanent magnet is used, not only is it difficult to design the magnetic characteristics and the shape / dimension for obtaining the optimum reproduction condition, but also variations in the characteristics are likely to occur, and correction thereof is also difficult.

On the other hand, a method of providing a coil for generating a DC bias magnetic field in the reproducing head can be considered, but this method also complicates the manufacturing process of the reproducing head and causes a high cost. Further, the bias magnetic field generating coil needs to be provided in the vicinity of a region of the magnetic material to which the recording signal magnetic field from the magnetic recording medium is applied more, that is, in an optimum position near the magnetic recording medium. It is very difficult to provide this coil at the optimum position because the magnetic body, the high frequency coil, and the like are present in a position close to the magnetic recording medium in the reproducing head.

[Object of the Invention]

The present invention has been made in view of such a conventional problem, and in a device for reproducing a magnetic recording signal by utilizing a change in a high frequency magnetic characteristic of a magnetic body due to a recording signal magnetic field from a magnetic recording medium, a reproducing head It is an object of the present invention to provide a magnetic reproducing device equipped with a means for effectively applying an appropriate DC bias magnetic field to a magnetic material without being restricted by the physical structure and manufacturing process of the above.

[Outline of Invention]

In order to achieve this object, the present invention supplies a direct current to a high-frequency coil provided in a high-frequency circuit in order to apply a high-frequency magnetic field to a magnetic material whose high-frequency magnetic characteristics change due to a recording signal magnetic field from a magnetic recording medium. Therefore, a DC bias magnetic field is generated from the coil and applied to the magnetic body.

〔The invention's effect〕

In the present invention, since the high-frequency coil included in the high-frequency circuit is used as it is as the DC bias magnetic field applying means, an appropriate DC bias magnetic field can be generated without using a permanent magnet or a dedicated coil for applying the DC bias magnetic field. Can be applied to. Therefore, the structure of the reproducing head is greatly simplified, and there are no restrictions on the arrangement when it is applied to an actual recording / reproducing apparatus, and a DC bias magnetic field is applied to the magnetic body at an optimum position close to the magnetic recording medium. Therefore, it is possible to easily obtain a reproduction output having a high level, a high S / N and little distortion.

That is, the recording signal magnetic field from the magnetic recording medium is generally concentrated near the surface of the medium, and the tendency becomes more remarkable especially when the recording wavelength is short. It is provided so that a high-frequency magnetic field is applied to a region near the surface of the medium, which is easily affected, and a change in the high-frequency magnetic characteristics in that region can be easily detected. Therefore, when the high frequency coil is used for applying the DC bias magnetic field as in the present invention, the DC bias magnetic field is also applied to the optimum position close to the magnetic recording medium made of a magnetic material, especially in the short wavelength region. This is convenient for improving the reproduction in the.

Example of Invention

FIG. 1 shows the structure of a magnetic reproducing apparatus according to an embodiment of the present invention. In the figure, a reproducing head is formed on a non-magnetic insulating head substrate 1 and has the following structure. That is, a thin-film magnetic body 2 made of ferrite, FE-Ni alloy, amorphous alloy, or the like is adhered and formed on the substrate 1 in the vicinity of the front end portion thereof, and a high-frequency coil is formed so as to overlap the front end portion of the magnetic body 2. The substantially U-shaped thin-film conductor 3 of FIG.

The magnetic body 2 and the thin film conductor 3 form an inductance element, and the resonance element (high frequency circuit) is configured by the inductance element and the resonance capacitor 4. One end side of this resonance circuit is grounded and the other end side is connected to a high frequency oscillator 6 via a high frequency coupling capacitor 5. The high frequency oscillator 6 oscillates at a frequency sufficiently higher than the frequency of the recording signal recorded on the magnetic recording medium 13, for example, a frequency of about 100 MHz or more. The other end of the resonance circuit is further connected to a detection circuit including a diode 7, a resistor 8 and a capacitor 9.

The other end of the thin film conductor 3 is connected to the DC power supply 12 via the resistor 10 and the choke coil 11. The DC power source 12 is for generating a DC bias magnetic field from the thin film conductor 3 by superimposing a high frequency from the high frequency oscillator 6 on the thin film conductor 3 and supplying a DC current. The resistor 10 and the choke coil 11 are connected to the DC power source 1
By separating the thin film conductor 3 and the thin film conductor 3 in terms of direct current, it is possible to prevent the Q of the resonant circuit from decreasing due to the leakage of a high frequency signal to the side of the direct current power supply 12.

The reproducing head configured as described above is arranged such that the end surface of the head substrate 1 on which the magnetic body 2 is formed faces the track 14 on the magnetic recording medium 13 as shown in the figure. When the magnetic recording medium 13 is run in the direction of the arrow in this state, the magnetic substance 2 causes the magnetic field of the recording signal from the magnetic recording medium 13, that is, the magnetic field due to the recording magnetization 15 from the track 14 on the medium 13 to change the high frequency magnetic characteristics. For example, the high frequency magnetic permeability and the loss term thereof change.

Here, since the high frequency signal from the high frequency oscillator 6 is supplied to the resonance circuit, a high frequency magnetic field is generated from the thin film conductor 3, and this high frequency magnetic field is applied to the magnetic body 2. As described above, the magnetic substance 2 changes its high-frequency magnetic characteristic due to the recording signal magnetic field, that is, the magnetic characteristic with respect to the high-frequency magnetic field emitted from the thin-film conductor 3, so that the change of the magnetic characteristic changes the resonance frequency or Q of the resonance circuit. As a result, the high frequency signal output changes. Therefore, by detecting the change of the high frequency signal output by the detection circuit, the magnetic recording medium 1
A reproduction output for the signal recorded on the above 3 will be obtained.

Here, the thin-film conductor 3 is also supplied with a direct current from the direct-current power supply 12 to generate a direct-current magnetic field, which is applied to the magnetic body 2 as a bias magnetic field. By applying the DC bias magnetic field, the change in the high frequency magnetic characteristics of the magnetic body 2 with respect to the recording signal magnetic field from the magnetic recording medium 13 is increased, and the linearity and the like are improved. As a result, the reproduction output has a large level and S / It is possible to obtain a signal with a low distortion ratio, which has a good N and is also excellent in linearity with respect to the recording signal magnetic field.

In this case, in order to apply a DC bias magnetic field to the magnetic body 2, a high frequency magnetic field is applied to the magnetic body 2 and a thin film conductor 3 as a high frequency coil for detecting a change in the high frequency magnetic characteristics of the magnetic body 2 is used. Since it is used, the structure of the reproducing head is remarkably simple and manufacturing is easy as compared with the case of using a permanent magnet or a coil dedicated to applying a bias magnetic field.

Furthermore, since the DC bias magnetic field can be applied to the same optimum area of the magnetic body 2 as the area to which the high frequency magnetic field is applied, that is, the area near the surface of the magnetic recording medium 13, the recording signal magnetic field from the magnetic recording medium 13 is applied. The change in the high-frequency magnetic characteristics due to the magnetic resonance enables effective detection. Therefore, particularly when reproducing a signal recorded at high density by short-wavelength recording, the recording signal magnetic field concentrated on the surface of the medium 13 can be detected with extremely high sensitivity, which greatly contributes to the improvement of the reproducing characteristic. To do.

FIG. 2 shows another embodiment of the present invention.
2 is replaced with an output variable type power supply circuit 16, and a feedback type DC bias magnetic field applying means for controlling the output current thereof according to the fluctuation of the reproduction output is constituted. By doing so, fluctuations in the reproduction output can be compensated by controlling the DC bias magnetic field, and more stable reproduction can be performed.

FIG. 3 shows still another embodiment of the present invention, in which the head substrate is partially filled with a non-magnetic dielectric material, or a magnetic material yoke 18 having an opening 17 is provided in a part as shown in the drawing. By interposing the non-magnetic thin film layer 19 between the magnetic body yoke 18 and the magnetic body 2, the magnetic body 2 and the magnetic body yoke 18 form a closed magnetic path for the recording signal magnetic field from the magnetic recording medium 13. It is an example when applied to a reproducing head having a structure. The other parts of the reproducing head are similar to those of the embodiment shown in FIG. 2 and are not shown.

According to this embodiment, the recording signal magnetic field from the magnetic recording medium 13 is absorbed up to the magnetic body 2 by the closed magnetic path formed by the magnetic body 2 and the magnetic yoke 18. The region to which the high frequency magnetic field is applied to the magnetic body 2 is the same as the region to which the DC bias magnetic field is applied, and the same effect as that of the previous embodiment can be obtained. In this embodiment, the feedback type DC bias applying means is constructed similarly to FIG. 2, but such a closed magnetic circuit structure can be taken even when a simple DC power source is used.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

[Brief description of drawings]

1 to 3 are diagrams showing the configuration of a magnetic reproducing apparatus according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Head substrate, 2 ... Magnetic body, 3 ... Thin film conductor (high frequency coil), 4 ... Resonance capacitor, 5 ... High frequency coupling capacitor, 6 ... High frequency oscillator, 7 ... Diode, 8 ... Resistor, 9 ... Capacitor, 10 ... resistance, 11 ... choke coil, 12 ... DC power supply, 13 ... magnetic recording medium, 14 ... track, 15 ... magnetization, 16 ... variable output power supply circuit, 17 ... aperture, 18 ... magnetic yoke, 19 ... non-magnetic thin film layer .

Claims (2)

[Claims] 1. A magnetic body whose high-frequency characteristics are changed by a recording signal magnetic field from a magnetic recording medium, and a magnetic body coupled to the magnetic body,
A high-frequency circuit including a high-frequency coil that applies a high-frequency magnetic field to the magnetic body by being supplied with a high-frequency signal, and a change in the high-frequency signal output due to a change in the high-frequency magnetic characteristics of the magnetic body from the high-frequency circuit is detected. A magnetic reproducing apparatus having means for obtaining a reproduced output of a signal recorded on the magnetic recording medium, comprising means for supplying a direct current to the high-frequency coil for applying a direct-current bias magnetic field to the magnetic body. A magnetic reproducing device characterized by the above. 2. A means for supplying a direct current to the high frequency coil, wherein the current value is controlled according to the fluctuation of the reproduction output level. Magnetic reproducing device.