JPH0414426B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field] The present invention provides a method for recording magnetic recording signals recorded on a magnetic recording medium using a soft magnetic film surface perpendicularly easily magnetized film (hereinafter referred to as "soft magnetic perpendicularly magnetized film") that is in a demagnetized state or a state close to it. The present invention relates to a magneto-optical readout film that is transferred to a magnetic domain pattern (referred to as a film) and a method for reading out the transferred magnetic domain signals using the magneto-optic effect.

[Prior Art] A ring-shaped magnetic head is known as a magnetic recording signal readout device that has been widely used in the past. This ring-shaped magnetic head requires a minimum
A recording track width of about 30 μm is required, and the upper limit of recording density is limited by this track width.

As a method to solve this problem, a method of optically reading out magnetically recorded signals has been proposed (see, for example, Japanese Patent Application Laid-open No. 59915/1983). In this method, as shown in FIG. 1, a soft magnetic perpendicularly magnetized film 2a, such as a magnetic garnet film, is placed close to a magnetic recording medium 1, such as a magnetic tape. As shown in FIG. 1, the labyrinth-like magnetic domains existing in a demagnetized state or a state close to it are moved in the direction perpendicular to the recording track 1b of the magnetic recording medium 1 by the leakage magnetic field generated from the recording signal of the magnetic recording medium 1. , to generate a striped magnetic domain pattern 2b whose width is modulated by the recording signal. This is called transcription. For the fixed soft magnetic perpendicular magnetization film 2a,
When the magnetic recording medium 1 moves, the striped magnetic domain pattern 2b aligned perpendicularly to the recording track moves on the perpendicular magnetization film 2a as the magnetic recording signal of the medium travels. Changes in the width of these striped magnetic domains, that is, magnetic domain signals, are read out using the magneto-optical effect.

However, this reading method has the following drawbacks.

As the wavelength of the signal recorded on the first magnetic recording medium becomes longer, the perpendicular component of the leakage magnetic field becomes weaker, and the labyrinthine magnetic domains can no longer be aligned, so the transferred magnetic domains become unstable and the original Unnecessary magnetic domains will appear in places where they shouldn't be. For example, when a signal with a recording wavelength of 50 μm is transferred to a magnetic garnet film with a magnetic domain period of 13 μm, unnecessary magnetic domains may be generated, and signals with an even longer recording wavelength will definitely generate unnecessary magnetic domains. As described above, correct transfer is not performed in a region where the recording wavelength is long, making it difficult to perform readout with a good signal-to-noise ratio.

Second, in order to read signals recorded at short wavelengths, it is necessary to use a magnetic garnet film whose magnetic domain period is equal to or shorter than the wavelength. However, when a magnetic garnet film with such a short domain period is in a demagnetized state or a state close to it, a large leakage magnetic field is required to align the labyrinthine magnetic domains into parallel striped magnetic domains, and furthermore, the magnetic recording medium Since the leakage magnetic field generated from a signal recorded at a short wavelength becomes weaker, it becomes difficult to align the maze-like magnetic domains to the striped magnetic domains, and the transfer in the short wavelength region becomes incomplete.

Thirdly, a plurality of tracks recorded on the magnetic recording medium 1 have a narrow track width of 20 μm or less and are spaced sufficiently apart from adjacent tracks (for example, longer than the length of the magnetic domain period of the magnetic garnet film used). When reading the signal of the recording track of a book,
Labyrinth-like magnetic domains remain between the tracks, which connect with the transferred striped magnetic domains, suppressing and deteriorating the running characteristics of the striped magnetic domains. In addition, it has a narrow track width and is close to the adjacent track (1/2 of the magnetic domain period).
When reading a signal from a track recorded in the following manner, the magnetic domain edge of the signal domain to be read is disturbed by or connected to the transferred signal domain of the adjacent track. As a result, a portion of the signal of an adjacent track is superimposed on the signal to be read, making it difficult to faithfully read out signals recorded at high track density with a good signal-to-noise ratio.

[Objective] Therefore, an object of the present invention is to provide a magnetic recording medium that responds faithfully even when the leakage magnetic field of a magnetic recording signal recorded on a magnetic recording medium is weak, and that is less susceptible to the influence of magnetic domains of adjacent tracks. An object of the present invention is to provide a magneto-optical readout film made of a soft magnetic perpendicular magnetization film.

Another object of the present invention is a magneto-optical reading method for transferring a signal recorded on the magnetic recording medium to the labyrinthine magnetic domains of such a soft magnetic perpendicularly magnetized film and optically reading out the transferred magnetic domain signals. Our goal is to provide the following.

[Structure of the Invention] In order to achieve the above object, the magneto-optical readout film of the present invention transfers signals magnetically recorded on a plurality of tracks on a magnetic recording medium to labyrinthine magnetic domains of a soft magnetic perpendicular magnetization film, In a magneto-optical readout film for optically reading out the magnetic domain signals of the transferred soft magnetic perpendicular magnetization film, the main component of the magneto-optical readout film is a soft magnetic material having a magnetic domain period approximately equal to the recording track spacing on the magnetic recording medium. A perpendicularly magnetized film is used, and a large number of linear magnetic anisotropies are introduced onto the film surface at intervals approximately equal to the magnetic domain period, and when the soft magnetic perpendicularly magnetized film is in a demagnetized state or a state close to it, It is characterized in that the labyrinth-like magnetic domains present therein are aligned in advance in a certain direction into a large number of parallel strip-like magnetic domains.

Furthermore, the magneto-optical readout method of the present invention transfers the signals magnetically recorded on a plurality of recording tracks on a magnetic recording medium to the labyrinth-like magnetic domain of the soft magnetic perpendicularly magnetized film, and In a magneto-optical readout method in which magnetic domain signals of an easily magnetized film are optically read out, a large number of parallel strip-shaped magnetic domains, which are pre-generated in a soft magnetic perpendicularly magnetized film at intervals approximately equal to the recording track spacing on a magnetic recording medium, form a recording track. The soft magnetic perpendicularly magnetized films are arranged so as to be parallel to the longitudinal direction and overlap with each other, and the width of the parallel strip magnetic domain is changed according to the magnetic recording signal recorded on each recording track. do.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

In FIG. 2, a magneto-optical readout film 2 whose main component is a soft magnetic perpendicularly magnetized film 2a according to the present invention, such as a magnetic garnet film, is arranged in the vicinity of the magnetic recording medium 1, and a magneto-optical readout device is installed, for example. This is an example of use as a video signal reproducing device. The magnetic recording medium 1 is, for example, a magnetic tape made of ordinary chromium dioxide, which runs at 50 m/s in the direction of the arrow in FIG.
It is assumed that a signal frequency-modulated by a video signal is recorded on the recording track 1b (FIG. 1) in a narrow track width.

The magneto-optical reading device has a laser light source 3,
The laser beam 3a is guided to a beam splitter 5 via a polarizing prism 4. The optical output from the beam splitter 5 is focused by a converging lens 6 onto the soft magnetic perpendicularly magnetized film 2a of the magneto-optical readout film 2. The reflected light emitted by the magneto-optical effect of the magneto-optical readout film 2 passes through the lens 6, is guided by the beam splitter 5 to the polarizing prism 7, is further incident on the photodetector 8, and is electrically transmitted from the signal output terminal 9. It is extracted in the form of a signal.

FIG. 3 shows a cross-sectional view of the magneto-optical readout film 2. As shown in FIG.
The soft magnetic perpendicular magnetization film 2a is a perpendicularly magnetized film that is transparent from the visible region to the infrared region and is formed on one main surface of the GdGa garnet substrate 2c with a thickness of 0.2 to 0.4 mm.
For example, (Y, Sm, Lu, Bi,
A magnetic garnet film such as Ca) ₃ (Fe, Ge) ₅ O ₁₂ with a small coercive force, for example 10e or less, is used. On the surface of this soft magnetic perpendicularly magnetized film 2a, for example, a magnetic garnet film, as shown in FIG.
Grooves 2g each having a width of about 1 μm and a length of about 500 μm are formed at intervals that almost match the magnetic domain period of the magnetic garnet film 2a. As a result, a potential well of magnetic energy is formed in the magnetic garnet film, and parallel strip-shaped magnetic domains are generated at equal intervals along the grooves 2g. Moreover, similar parallel strip-shaped magnetic domains may be generated by forming many strip-shaped patterns by ion implantation.

In FIG. 3, an anti-reflection coating 2d is formed on the other main surface of the GdGa garnet substrate 2c. On the other hand, on the main surface of the magnetic garnet film 2a facing the magnetic recording medium 1, a metal film, for example, a reflective film 2e of Al, with a thickness of about 0.2 μm is deposited. The light transmitted through the garnet film 2a is almost completely reflected. A protective film 2f having a thickness of about 0.5 μm is further formed on the reflective film 2e. As this protective film 2f, for example,
Use _SiO2 membrane.

Further, the layer consisting of the reflective film 2e and the protective film 2f may be formed of a dielectric reflective film having a thickness of 1 to 2 μm, which is made by laminating multiple dielectric films such as TiO ₂ and SiO ₂ . can.

a magnetic recording medium 1 having a plurality of recording tracks;
For example, as shown in FIG. 5A, it is assumed that two signals having different recording wavelengths are recorded on tracks 1b1 and 1b2 of a magnetic tape having a three-channel multitrack, and no signal is recorded on track 1b3. On the other hand, in the soft magnetic perpendicularly magnetized film 2a formed on the magneto-optical readout film 2, for example, a magnetic garnet film, parallel strip-shaped magnetic domains 2h1, 2h2, and 2h3 having appropriate magnetic domain widths are formed in advance to form recording tracks 1b1, 1b2, and 1b3. It is assumed that they are formed at the same intervals.

Here, the magnetic tape 1 and the magnetic garnet film 2a
the recording track 1b1 of the magnetic tape 1.
1b3 and the parallel strip-shaped magnetic domains 2h1 to 2h3 in the magnetic garnet film 2a are arranged in parallel and overlapping, the parallel strip-shaped magnetic domains 2h1 and 2h2 are affected by the leakage magnetic field generated from the corresponding tracks 1b1 and 1b2 on which signals are recorded. Therefore, the magnetic domain width is partially expanded or decreased. As a result, as shown in FIG.
That is, a magnetic domain signal is formed. If the magnetic tape 1 is moved, for example, from left to right with respect to the fixed magneto-optical readout film 2, the part where the magnetic domain width has been widened (or the part where it has been shortened) will also move to the left. Move to the right. At this time, there is no change in the domain width of the parallel band-shaped magnetic domain 2h3 for the track 1b3 on which no signal is recorded.

Note that the recording tracks 1b1 to 1 of the magnetic tape 1
b3 and the parallel strip magnetic domains 2 in the magnetic garnet film 2a
h1 to 2h3 are parallel to each other, but their relative positions are set perpendicularly to the recording track by 1/1 of the track width.
Shift them by about 2 to 1/3 so that they overlap,
As shown in FIG. 5b, the same effect as described above can be obtained even if the width of the parallel strip magnetic domains is asymmetrically widened or shortened.

As in the configuration example shown in FIG. 6, a configuration may be adopted in which signals on multiple tracks are simultaneously read out using multiple light beams.

That is, FIG. 6 shows an embodiment in which the magneto-optical readout film 2 according to the present invention is applied to, for example, a three-channel multitrack readout device. In FIG. 6, three independent laser light sources or
Three laser beams 11 obtained by combining one laser light source and a diffraction grating
passes through the polarizing prism 4, the beam splitter 5, and the converging lens 6, and forms, for example, three adjacent strip-shaped magnetic domains 2h1 and 2h2 in the soft magnetic perpendicularly magnetized film 2a provided on the magneto-optical readout film 2, such as a magnetic garnet film. , converges on 2h3 (Fig. 5a
reference). The magnetic recording medium 1 includes signal tracks 1b1,
1b2, 1b3, 1b4, 1b5, and 1b6 are arranged. The light transmitted through the soft magnetic perpendicular magnetization film 2a of the magneto-optical readout film 2 passes through the reflection film 2e (see FIG. 3).
, and reaches the beam splitter 5 again through the same path. By passing through the soft magnetic perpendicularly magnetized film 2a twice, the reflected beam is applied by the Faraday effect according to the magnitude of the magnetization of the parallel band-shaped magnetic domain, and the rotation angle on the parallel plane varies. It will change in response to the truck signal. After these beams pass through the polarizing prism 7,
Three photodetectors 8a, 8 by converging lens 10
electrical signals 9a, 9b, 9
converted to c.

Signals were recorded on 10 recording tracks with a track width of 1.5 μm and an interval of 3 μm on the recording medium, and 10 recording tracks with a width of 1.5 μm and an interval of 3 μm were placed in a Bi-substituted garnet film with a magnetic domain period of 3 μm as a magneto-optical readout film. Generates parallel strip magnetic domains. According to the magneto-optical reading film of the present invention, it was possible to read signals of each track having a recording wavelength of 3 to 200 μm. Therefore,
When the traveling speed of the magnetic recording medium is 50 m/s or more,
Signal transfer speeds of 20Mb/s or more can be achieved. With this, if 10-channel multitrack playback is performed, a high-speed signal transfer of 200 Mb/s can be achieved in total. Further, the amount of crosstalk between adjacent channels at this time was -40 db or less.

[Effect] According to the present invention, when transferring a magnetic recording signal, instead of aligning maze-like magnetic domains existing in a soft magnetic perpendicularly magnetized film according to a signal recorded on a magnetic recording medium, , Parallel band-shaped magnetic domains previously generated in a soft magnetic perpendicularly magnetized film are placed parallel to the longitudinal direction of the recording track of a magnetic recording medium, and the width of the magnetic domain is changed depending on the signal recorded on the magnetic recording medium. and read out the signal. Therefore,
In the present invention, since the plurality of recording tracks and parallel strip magnetic domains do not intersect, the influence of adjacent tracks is small.

Furthermore, even if the leakage magnetic field generated by the signal recorded on the magnetic recording medium becomes small, it is faithfully transferred to the soft magnetic perpendicular magnetization film as a magnetic domain signal regardless of the recording wavelength, so the amplitude of the read signal is The signal may be read out, but the signal may be read out. Therefore, the signal recorded on the magnetic recording medium
Even at a long recording wavelength of 200 μm, the width of the parallel strip magnetic domains changes faithfully in response to the signal magnetic field, making it possible to read long wavelength signals. This also applies to signals with wavelengths shorter than the magnetic domain period. In addition, the track width of a signal suitable for readout is the width of the parallel band-shaped magnetic domains generated in a soft magnetic perpendicularly magnetized film, for example, 1/2 of the magnetic domain period in the case of a magnetic garnet film, so a very high track width is required. It is possible to read out signals recorded at high density.

Furthermore, in the conventional example, when a magnetic recording medium is run, striped magnetic domains oriented perpendicular to the recording track direction (same as the running direction) of the medium move from one end of the soft magnetic perpendicular magnetization film to the other. If there are factors such as lattice defects in the magnetized film that impede magnetic domain movement, the labyrinth-like domains will get stuck in that area, deteriorating the running characteristics.
In the present invention, when the magnetic recording medium is running, only the width of the strip-shaped magnetic domains parallel to the running direction changes, so that fast changes can be followed, and the effects of lattice defects and the like are also reduced.

As explained above, the optical reading film according to the present invention can reproduce a wide band signal recorded in a narrow track width on a magnetic recording medium with a good signal-to-noise ratio. Furthermore, since the reading method according to the present invention is a magnetic flux response type reading, the moving speed of the magnetic recording medium and the amplitude of the read signal are unrelated. Therefore, the quality of the read signal does not deteriorate even if the magnetic recording medium is read out by driving it at a moving speed different from that during recording, so this can be used to generate video or audio signals for the purpose of converting the time axis. Special playback, etc. are possible.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of striped magnetic domains transferred to a soft magnetic film surface-perpendicular easily magnetized film by a conventional method, FIG. 2 is a diagram showing an example of the configuration of a magneto-optical readout device according to the present invention, and FIG. A cross-sectional view showing an example of a magneto-optical readout film according to the present invention, FIG. 4 is an explanatory diagram of an example of generating parallel strip-like magnetic domains in a soft magnetic film with perpendicular easy magnetization, and FIG. 5a is a signal readout film according to the present invention. FIG. 5b is a diagram showing the principle of signal readout according to another example, and FIG. 6 is a diagram showing the principle of signal readout according to another example of the present invention. It is a line diagram showing an example of composition. 1... Magnetic recording medium, 1a... Magnetic layer, 1b...
...Recording track, 2...Magneto-optical readout film, 2a...
... Soft magnetic film surface perpendicular easy magnetization film (magnetic garnet),
2b... Striped magnetic domain pattern, 2c... GdGa garnet substrate, 2d... Non-reflective coating, 2e... Reflective film, 2f... Protective film, 2g... Groove, 3... Laser light source, 3a... Laser Beam, 4...Polarizing prism, 5...Beam splitter, 6...Converging lens, 7...Polarizing prism, 8, 8a to 8c...Photodetector, 9, 9a to 9c...Signal output terminal, 10
...Convergent lens, 11...Laser beam, 1b1
~1b6... Recording track, 2h1, 2h2...
Parallel strip magnetic domain subjected to width modulation, 2h3... Parallel strip magnetic domain not subjected to width modulation.

Claims (1)

[Claims] 1. Transferring signals magnetically recorded on a plurality of tracks on a magnetic recording medium to labyrinth-like magnetic domains of a soft magnetic film with easy magnetization perpendicular to the surface of the soft magnetic film, and transferring the transferred easy magnetization perpendicular to the soft magnetic film surface. In a magneto-optical readout film for optically reading the magnetic domain signals of the film, a magnetic field is formed on the film surface of a soft magnetic film surface-perpendicular easily magnetized film having a magnetic domain period approximately equal to the recording track spacing on the magnetic recording medium. A magneto-optical readout film characterized in that a large number of parallel strip-shaped magnetic domains are provided at intervals in a certain direction. 2. The signals magnetically recorded on a plurality of tracks on a magnetic recording medium are transferred to the labyrinthine magnetic domains of the soft magnetic film with easy magnetization perpendicular to the surface of the soft magnetic film, and the transferred magnetic domain signals of the soft magnetic film with easy magnetization perpendicular to the surface of the soft magnetic film are optically transferred. In the magneto-optical readout method, the plurality of parallel strip-shaped magnetic domains previously generated in the easily magnetized film perpendicular to the soft magnetic film surface are arranged in the longitudinal direction of the recording track at intervals approximately equal to the recording track interval on the magnetic recording medium. The soft magnetic perpendicularly magnetized film is arranged so as to be parallel to and overlap with the magnetic field, and the width of the parallel strip magnetic domain is changed depending on the magnetic recording signal recorded on each recording track. Magnetic reading method.