JPS63166001A - Magnetic reproducing device - Google Patents

Abstract

PURPOSE:To improve reproducing sensitivity and a frequency character without increasing noise, by setting the film thickness of an area being connected to a resonance circuit of magnetic material film larger than that of the area which detects a signal magnetic field. CONSTITUTION:The magnetic material film 1 consists of the area 11 connected to the coil 2 of the resonance circuit 4 and the area 12 which detects the signal magnetic field from a magnetic recording medium, and the film thickness of the coupling area 11 is formed larger than that of the detecting area 12. Therefore, the film thickness of the detecting area 12 is thin, and the diamagnetic field of the magnetic material film 1 in a direction of length is suppressed, thereby, the signal magnetic field H can be detected with resulting superior sensitivity. Also, the coupling area 11 of the magnetic material field 1 and the coil 2 of the resonance circuit 4 are coupled electromagnetically, and is taken out as a reproducing signal output Vout via a peak detection circuit 10. In this case, the noise of the output is increased when the coil 2 is coupled with the magnetic material film 1 and it depends on the film thickness of the coupling area 11. In such a way, it is possible to improve the reproducing sensitivity and the frequency characteristic and to effectively reduce the noise included in the output of a reproducing signal.

Description

[Detailed Description of the Invention] CObject of the Invention] (Industrial Field of Application) The present invention relates to an apparatus for reproducing signals recorded on a magnetic recording medium, and in particular, the present invention relates to a device for reproducing signals recorded on a magnetic recording medium. The present invention relates to a magnetic reproduction device that performs reproduction by detecting changes in high frequency magnetic characteristics.

(Prior Art) In an apparatus for reproducing signals recorded on a magnetic recording medium, as a method extremely suitable for high-density recording and reproducing, a signal magnetic field based on a signal recorded on a magnetic recording medium is transmitted to a high-frequency magnetic field of a magnetic film. A method has already been filed in which a change in characteristics is detected, for example, a change in the real part of high-frequency magnetic permeability and a change in its imaginary part, and reproduction is performed using this change in high-frequency magnetic characteristics (Japanese Patent Laid-Open No. 57-36407). etc).

FIG. 6 shows a prior art configuration of a magnetic reproducing device based on this method, in which a resonant circuit 4 consisting of a coil 2 made of a thin film conductor coupled to a magnetic film 1 and a resonant capacitor 3 is shown. A high frequency signal with a frequency of, for example, about 600 to 700 MH2 is supplied from the high frequency oscillator 5 via the coupling capacitor 6, and the high frequency permeability of the magnetic body 111 changes due to the signal magnetic field H from the magnetic recording medium (not shown). A detecting circuit, for example, a peak detecting circuit 1o composed of a diode 7, a capacitor 8, and a resistor 9, detects a change in the high-frequency signal output of the resonant circuit 4 according to the response, and outputs a reproduced signal corresponding to the signal recorded on the magnetic recording medium. ■It is something to get out.

In other words, the signal magnetic field H from the magnetic recording medium causes the magnetic material! When the high-frequency magnetic characteristics of 11 change, the resonant frequency and Q of the resonant circuit 4 change, and the high-frequency signal supplied to the resonant circuit 4 undergoes amplitude modulation, so the signal that has undergone this amplitude modulation is peak-detected. By detecting the signal in the circuit 10, a reproduced signal output VOut can be obtained.

In such a magnetic reproducing device, the reproduced signal output yo
It is known that the size of ut depends on the film thickness d of the magnetic material 1111. That is, when the film thickness d is large, the demagnetizing field in the direction of the length h of the magnetic film 1 increases, and the signal magnetic field H from the magnetic recording medium cannot be detected with high sensitivity.
If the film thickness d is very small compared to the width W and length h of , this demagnetizing field becomes small and good reproduction with high sensitivity becomes possible.

Furthermore, when the frequency characteristics of the reproduced signal output vout when the magnetic recording medium is moved in the direction of the film thickness d of the magnetic film 1 are measured, it is found that due to an effect similar to the gap loss of a ring-type magnetic head, the film thickness d The reproduced signal output v out sharply decreases at a frequency corresponding to approximately the same recording wavelength. In other words, the smaller the film thickness d, the more signals with shorter recording wavelengths can be reproduced.

In this way, from the perspective of reproduction sensitivity and frequency characteristics, magnetic material 1
It is preferable that the film thickness d of No. 11 is smaller. However, according to research conducted by the present inventors, it has been found that when the film thickness d of the magnetic film 1 is reduced, the noise included in the reproduced signal output vout increases.

FIG. 7 shows the noise versus frequency characteristics when a Ni--Fe alloy thin film is used as the magnetic film 111 with various thicknesses d of the magnetic film 1. As shown in the figure, the noise increases as the film thickness d decreases from 0.4 μm to 0.2 μm to 0.1 μm.

(Problems to be Solved by the Invention) In this way, in conventional magnetic reproducing devices, if the thickness of the magnetic film that detects the signal magnetic field from the magnetic recording medium is reduced, the reproducing sensitivity and frequency characteristics improve. , there is a problem in that the noise included in the reproduced signal output increases.

Accordingly, an object of the present invention is to provide a magnetic reproducing device that can improve reproduction sensitivity and frequency characteristics without increasing noise.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a magnetic film whose high frequency magnetic properties change by detecting a signal magnetic field based on a signal recorded on a magnetic recording medium, and a magnetic film that changes high frequency magnetic properties by detecting a signal magnetic field based on a signal recorded on a magnetic recording medium. a resonant circuit that is coupled to and applies a ^-frequency magnetic field to the magnetic film by being supplied with a high-frequency signal, and whose high-frequency signal output changes as the high-frequency magnetic characteristics of the magnetic film change; In a magnetic reproducing device equipped with a detection circuit that detects a change in the high frequency signal output of this resonant circuit and reproduces a signal recorded on a magnetic recording medium, the film thickness of the region of the magnetic film that is coupled to the resonant circuit. is larger than the film thickness of the region where the signal magnetic field is detected.

(Function) In the present invention, since the region of the magnetic film that detects the signal magnetic field from the magnetic recording medium has a small film thickness, the demagnetizing field is small and the signal magnetic field is detected with high sensitivity. Furthermore, a small film thickness in this region is advantageous in terms of frequency characteristics.

On the other hand, the main components of noise included in the reproduced output appear only when a resonant circuit is coupled to the magnetic film and a high-frequency magnetic field is applied to the magnetic film, according to studies by the present inventors. Therefore, the noise is mainly caused by the magnetic material IW!
;Of 4, it occurs in the region that couples with the resonant circuit. Therefore, if the film thickness in this region is increased, the noise that depends on the film thickness of the magnetic film will be reduced.

(Example of Practical Theory) FIG. 1 shows the configuration of a magnetic reproducing device according to an embodiment of the present invention. A resonant circuit 4 (high-frequency circuit) is configured, and a high-frequency oscillator 5 is connected to a high-frequency oscillator 5 via a coupling capacitor 6 to form a resonant circuit 4 (high-frequency circuit).
The high frequency signal output of the resonant circuit 4 is performed by supplying a high frequency signal with a very high frequency such as 0 to 700 MH2, and responding to changes in high frequency magnetic properties such as high frequency permeability of the magnetic material 111 due to the signal magnetic field H from the magnetic recording medium. A change in is detected by a detection circuit, for example, a peak detection circuit 10 composed of a diode 7, a capacitor 8, and a resistor 9,
Playback output corresponding to the signal recorded on the magnetic recording medium
The basic configuration of obtaining ut is the same as the conventional device shown in FIG.

The magnetic film 1 and the coil 2 are formed on a reproducing head substrate (not shown) using III film technology.

Here, the magnetic body ii has a region 11 that couples with the coil 2 of the resonant circuit 4 (hereinafter referred to as the coupling region) and a region that detects the signal magnetic field from the magnetic recording medium (hereinafter referred to as the detection region).
12, and the film thickness of the bonding region 11 is the detection slope i*12
It is larger than the film thickness of .

With this configuration, since the detection area 12 has a small film thickness, the demagnetizing field in the length direction of the magnetic body 111 is suppressed, so that the signal magnetic field H can be detected with high sensitivity, and the signal magnetic field H can be detected with a shorter recording wavelength. can be played. That is, good reproduction sensitivity and frequency characteristics can be obtained.

On the other hand, since the film thickness of the coupling region 11 is large, noise included in the reproduced signal output Vout is reduced.

That is, the magnetic body WA1 is magnetized by the signal magnetic field H, and the resulting change in the high frequency magnetic characteristics of the coupling region 11 is caused by the electromagnetic coupling between the coupling region 11 of the magnetic body Ill and the coil 2 of the resonant circuit 4, which causes resonance. It is detected as a change in the resonant frequency or Q of the circuit 4, and this change is taken out via the peak detection circuit 10 as a reproduced signal output ■Out. In this case, the observed output noise is caused by connecting the coil 2 to the magnetic material 111.
For example, if the high-frequency oscillator 5 is connected to the coil 2 and the coil 2 is separated from the magnetic material ll11 as shown in the figure, the observed output noise will be smaller (of course, the signal components are not observed). From this, it is inferred that the main component of noise is generated from the relationship shown in FIG. 7 depending on the film thickness of the coupling region 11, which is the part where the electromagnetic coupling between the magnetic film 1 and the coil 2 is strong. . Therefore, by increasing the thickness of the coupling region 11, the noise contained in the reproduced signal output vout can be effectively reduced.

Note that the change in the high frequency magnetic properties of the magnetic film 1 due to the signal magnetic field H affects not only the detection region 12 but also the bond chain li! 11, thereby causing a change in the high frequency magnetic properties of the resonant circuit 4.
However, the above-mentioned suppression effect of the demagnetizing field (reproduction sensitivity to short wavelength recorded signals) and frequency characteristics are such that the detection region 12, that is, the signal magnetic field H is strongly detected. Since it largely depends on the film thickness of the region, even if the film thickness of the bonding chain [11 is large, the reproduction sensitivity and frequency characteristics are not adversely affected.

The magnetic material 111 in which the coupling region 11 and the detection slope 1J112 have different thicknesses can be obtained, for example, by the method shown in FIGS. 2 and 3. In FIG. 2, the entire magnetic material 111 is formed by vapor deposition, sputtering, etc. to the thickness of the coupling region 11, and then only the detection region 12 is formed by etching, reverse sputtering, ion milling, etc. until the required film thickness is achieved. This is a method to make it thinner.

FIG. 3 shows that after the entire magnetic film 1 has been formed to the thickness of the detection region 12, a second layer of magnetic film 1 is further formed on the coupling region 11.
This is a method of selectively forming 3.

In this case, the second layer magnetic material 1113 may be made of the same material as the magnetic material 1111, but since it is provided in the coupling region 11, it is sufficient that it is a soft magnetic material made of a different material from the detection region 12.

FIG. 4 shows another embodiment of the present invention, in which a coupling region 11 and a detection region 12 are formed in the shape of a spider, and are magnetically coupled by partially overlapping them, for example. It is something. In this case, the coupling region 11 and the detection region 12 may be made of the same material or may be made of different materials.

FIG. 5 shows yet another embodiment of the present invention, in which a magnetic recording medium is arranged on a base 1i121 with a high magnetic permeability layer 2
This is the case of a perpendicular magnetic recording medium 20 in which a magnetic recording layer 23 having an axis of easy magnetization in a direction perpendicular to the film surface is formed with a magnetic recording layer 23 interposed therebetween.

When reproducing a signal recorded on such a perpendicular magnetic recording medium 20, it is necessary to A magnetic yoke 14 is interposed between the magnetic material 111 and the medium 20, and a magnetic circuit is constituted by the magnetic material 111, the high magnetic permeability lining layer 22, and the magnetic material yoke 14.

It is known that when such a magnetic circuit is formed, the demagnetizing field in the detection region 12 of the magnetic body 111 becomes smaller.
In order to improve the frequency characteristics, it is necessary to make the film thickness of the detection region 12 sufficiently small. Therefore, in this embodiment as well, the thickness of the coupling region 11 is made larger than the thickness of the detection region 12, thereby reducing noise based on the same principle as described above.

The present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] According to the present invention, the signal magnetic field from the magnetic recording medium is detected, and the film thickness of the coupling region of the resonant circuit of the magnetic film coupled to the resonant circuit is determined by the thickness of the film in the region where the signal magnetic field is detected. By making it thicker than the thickness, it is possible to improve the reproduction sensitivity and frequency characteristics, and at the same time, effectively reduce the noise contained in the reproduction signal output.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a magnetic reproducing device according to an embodiment of the present invention, FIGS. 2 and 3 are diagrams for explaining a method of forming a magnetic film in the same embodiment, and FIGS. 5 is a block diagram of a magnetic reproducing device according to another embodiment of the present invention, FIG. 6 is a block diagram of a conventional magnetic reproducing device, and FIG. 7 is a block diagram of a magnetic film in a conventional magnetic reproducing device. FIG. 3 is a diagram showing the relationship between film thickness and noise. DESCRIPTION OF SYMBOLS 1... Magnetic film, 2... Coil, 3... Resonant capacitor, 4... Resonant circuit, 5... High frequency oscillator,
6... Coupling capacitor, 7... Diode, 8...
... Capacitor, 9... Resistor, 10... Peak detection circuit (detection circuit), 11... Coupling area, 12... Detection area, 13... Second layer magnetic material control, 14... - Magnetic material yoke, 20... Perpendicular magnetic recording medium, 21... Base layer, 22... Backing high permeability layer, 23... Magnetic recording layer. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (6)

[Claims] (1) A magnetic film whose high-frequency magnetic properties change by detecting a signal magnetic field based on a signal recorded on a magnetic recording medium, and a magnetic film that is coupled to this magnetic film and is supplied with a high-frequency signal. A high-frequency magnetic field is applied to the magnetic recording medium, and a resonant circuit whose high-frequency signal output changes as the high-frequency magnetic characteristics of the magnetic film changes, and a change in the high-frequency signal output of this resonant circuit is detected to detect the magnetic recording medium. a detection circuit for reproducing a signal recorded on a magnetic reproducing device, the film thickness of a region of the magnetic film coupled to the resonant circuit;
A magnetic reproducing device characterized in that the thickness of the signal magnetic field is greater than that of a region where the signal magnetic field is detected. (2) The magnetic film must have a region that detects the signal magnetic field and a region that couples with the resonant circuit integrally formed, and the region that detects the signal magnetic field must be thinned by etching, reverse sputtering, ion milling, etc. A magnetic reproducing device according to claim 1, characterized in that: (3) The magnetic film selectively has two regions that couple with the resonant circuit.
The magnetic reproducing device according to claim 1, characterized in that it is formed in a layered structure. (4) The second region in the region coupled to the resonant circuit of the magnetic film
4. The magnetic reproducing device according to claim 3, wherein the layer is made of a soft magnetic material. (5) Claims characterized in that the magnetic film has a region that couples with a resonant circuit and a region that detects a signal magnetic field are formed separately, and these two regions are magnetically coupled. 2. The magnetic reproducing device according to item 1. (6) A magnetic yoke according to claim 1, characterized in that a magnetic yoke is provided between the end of the magnetic film on the side opposite to the magnetic recording medium and the magnetic recording medium. playback device.