JP2000021041A - Floating type magnetic head device, signal reproducing method and recording and reproducing method using the head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a floating type magnetic head device with which a reproduced output is sufficiently obtained and the detection of the signals, which exceed an optical diffraction limit, is made possible. SOLUTION: An optical system having a numerical aperture NA>=1 is arranged on a floating slider 1 and a magneto-optical film 3 having a magneto- optical effect is formed at the focal position of the system. While reproducing the information signals of the magnetic disk, on which a vertically magnetized film is formed, the magnetization of the vertically magnetized film is transferred to the film 3 and read by the system having the numerical aperture NA>=1, thus the information recorded on the magnetic disk is reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel flying magnetic head for detecting information from a magneto-optical film which is magnetostatically coupled to a magnetic film formed on a magnetic disk. The present invention relates to a signal reproducing method and a recording / reproducing method used.

[0002]

2. Description of the Related Art The recording density of a magnetic disk has been rapidly increasing in recent years. At present, the highest density of a hard disk is determined by the performance of a magnetic head for signal detection and recording. It's not too much to say.

Under these circumstances, an MR head utilizing the magnetoresistance effect has been developed and is becoming the mainstream as a high-performance reproducing head. However, even if this MR head is used, if the track pitch becomes several μm or less, the output becomes insufficient. Is a problem.

To improve this, a magnetic head using a magnetoresistive element having a giant magnetoresistive effect, a so-called GMR head, has been put to practical use. On the other hand, there is also a problem in the process of forming the recording coil, and it is difficult to achieve a submicron track pitch.

[0005] Further, for magnetic disks (hard disk media), the areal density of the in-plane magnetic film is about to reach the limit due to thermal fluctuation, and in order to overcome this, the use of a perpendicular magnetic film has been proposed. I have.

However, when the perpendicular magnetization film is used as the recording layer, various problems such as noise of a hard disk medium and a so-called demagnetization effect remain, and it has not yet been put to practical use.

On the other hand, a magneto-optical disk uses a perpendicular magnetization film and is an exchange-coupling amorphous film, so that there is a margin up to the limit due to thermal fluctuations. There is a diffraction limit determined by a number NA.

As techniques for overcoming this, several magnetic super-resolution techniques have been proposed, but none of them have been put to practical use. This is one of the causes of magnetic mask instability, reliability, a reduction in reproduction power margin, and signal output.

[0009] Methods of optically focusing light using an optical system having a high NA or a near-field optical system (a so-called near-field optical system) have been studied in various fields. It has major drawbacks such as difficulty in assembling and susceptibility to dust and scratches. Further, the near-field optical system has a disadvantage that the effective NA is reduced due to loss at the interface with the air layer.

[0010] Several methods have been studied in which an optical fiber or a waveguide is incorporated into a floating head, and a spot size that cannot be obtained with an ordinary lens is realized by bringing the fiber end or the waveguide end close to the magneto-optical disk. This also has basically the same disadvantages as the high NA optical system.

[0011]

As described above, it has become increasingly difficult to increase the density of magnetic disks and magneto-optical disks even further, and to develop new technologies that overcome the above-mentioned limitations. Is desired.

Accordingly, the present invention has been proposed in view of such a conventional situation. It is an object of the present invention to provide a recording / reproducing system using a perpendicular magnetization film or an in-plane magnetization film to stably obtain a sufficient reproduction output. It is an object of the present invention to provide a flying magnetic head device capable of detecting a signal exceeding an optical diffraction limit and further providing a signal reproducing method and a recording / reproducing method.

[0013]

In order to achieve the above-mentioned object, a flying magnetic head device according to the present invention is provided with an optical system having a numerical aperture NA ≧ 1 on a flying slider and having a focal position at its focal position. A magneto-optical film having a magneto-optical effect is formed.

Further, according to the signal reproducing method of the present invention, when reproducing an information signal of a magnetic disk on which a perpendicular magnetization film is formed, an optical system having a numerical aperture NA ≧ 1 is arranged on a flying slider. Using a floating magnetic head device in which a magneto-optical film having a magneto-optical effect is formed at a focal position, the magnetization of the perpendicular magnetic film is transferred to the magneto-optical film, and is transferred to an optical system having a numerical aperture NA ≧ 1. The information signal recorded on the magnetic disk is reproduced by reading in the step (1).

Further, according to the recording / reproducing method of the present invention, when recording / reproducing an information signal with respect to a magnetic disk having a perpendicular magnetization film formed thereon, an optical system having a numerical aperture NA ≧ 1 is arranged on a flying slider. At the same time, using a floating magnetic head device in which a magneto-optical film having a magneto-optical effect is formed at the focal position, the magnetization of the perpendicular magnetic film is transferred to the magneto-optical film, and the numerical aperture NA ≧ 1. The information signal recorded on the magnetic disk is reproduced by reading with the optical system described above, and the focal position of the optical system having the numerical aperture NA1 is shifted to a position deviated from the magneto-optical film, thereby opening the aperture in the perpendicular magnetization film. The optical system is characterized by directly irradiating light from an optical system having several NA ≧ 1, that is, a near-field optical system, and thermally recording an information signal.

By using a near-field optical system (near-field optical system), it is possible to reproduce a signal exceeding the diffraction limit of the conventional optical system. In the case of direct reading, problems such as a decrease in the effective NA due to loss in the air layer, optical instability, dust, scratches, and the like become problems.

In the present invention, a magneto-optical film is formed at the focal position of the near-field optical system, and the signal of the perpendicular magnetic film is transferred to and read from the magneto-optical film. In addition, the optical system has an ideal numerical aperture NA ≧ 1, and since the optical system is closed, stable detection is always possible and is resistant to dust and scratches.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a flying magnetic head device to which the present invention is applied.

In the flying magnetic head device of the present invention, for example, as shown in FIG. 1, a solid immersion lens in which the slider 1 itself is formed of an optical material and one end of which constitutes an optical system having a numerical aperture NA ≧ 1. 2 is formed integrally, and a magneto-optical film 3 is formed at a focal position of the solid immersion lens 2.

The slider 1 is supported by a suspension 4 as in the case of a so-called floating type magnetic head for a hard disk. For example, rails are formed on a surface facing a magnetic disk (or a magneto-optical disk). Has a function of imparting buoyancy so as to float at a predetermined interval (flying amount) from the magnetic disk surface with the rotation of.

The solid immersion lens 2 constitutes an optical system having a numerical aperture NA ≧ 1, and plays a role of condensing a laser beam or the like for reading. In the case where a lens for condensing light on the solid immersion lens 2 is used as a separate body, as shown in FIG.
The condenser lens 5 can be formed separately from the slider 1. Of course, as shown in FIG. 3, both the condenser lens 5 and the solid immersion lens 2 can be incorporated in the slider 1.

In an optical system having a numerical aperture NA larger than 1,
In the case of using a near-field optical system (a so-called near-field optical system), information is detected by exudation light.
The distance between the disk and the end face of the lens becomes very short. At this time, the amount of transmitted light strongly depends on the distance between the disk and the end face of the lens due to the light interference, and if the distance is not maintained stably, the amount of detected light fluctuates. Also, the amount of transmitted light
The loss is large with respect to the incident light amount. Furthermore, the loss of the high NA component in the air layer between the disk and the end face of the lens lowers the effective NA and increases the spot size, thereby deteriorating the resolution.

Therefore, in the present invention, information is detected by the reflected light from the magneto-optical film 3. In this case, it is optically very stable, the output is large, and the focused spot size remains small.

When the optical system of NA ≧ 1 is integrated with the slider 1, no focus servo is required.
The tracking servo is realized by, for example, a sample servo method.

Alternatively, a spot is divided into three beams by a diffraction grating, a magneto-optical film 3 is formed only around the main spot, side spots are transmitted, and focusing and tracking are performed using the returned light. Etc. can also be adopted.

On the other hand, the magneto-optical film 3 transfers information (recording marks) recorded on the magnetic disk by magnetostatic coupling. Here, the magneto-optical film 3 is an in-plane magnetized film at room temperature and is heated in the vertical direction by heating. A magneto-optical film is used which exhibits magnetic field sensitivity to the magnetization of the optical system and which is sensitive to the external magnetic field only in a part of the light spot of the optical system of NA ≧ 1. As a result, signal reproduction using magnetic super-resolution called center aperture detection (CAD) is possible.

Therefore, for the magneto-optical film 3, for example, an alloy material containing Gd and a transition metal (TM) such as Fe or Co, or an alloy material containing Gd, a transition metal and an additive is used. Specifically, GdFeCo and the like can be mentioned.

In the case where the magnetic super-resolution is not used, the magneto-optical film 3 may be a perpendicular magnetic film having a soft magnetic characteristic and a magneto-optical effect.

The magneto-optical film 3 may be formed on the entire surface of the solid immersion lens 2 (when integrated with the slider 1, the entire bottom surface of the slider 1). Or a boundary may be formed near the focal point, or a stripe may be formed. As described above, when a spot is divided into three beams by a diffraction grating and tracking servo is performed by a side spot, a film having a diameter of several μm is formed only at a focal point, or a film is formed in a stripe shape and a side spot is formed. Must be directly applied to the magnetic disk.

As described above, the signal reproduction can be performed by transferring the information signal of the magnetic disk to the magneto-optical film 3 and reading the recording mark transferred to the magneto-optical film 3 by an optical system of NA ≧ 1. Recording can be performed by a method in which a recording coil is installed to perform magnetic recording similarly to a conventional hard disk, or a method in which thermomagnetic recording is performed similarly to magneto-optical recording (MO).

In order to realize the latter, light must be transmitted to the disk during recording. Therefore, the following two methods can be cited as methods for realizing this.

A. A magneto-optical film is formed only near the focal point on the bottom surface of the lens or the bottom surface of the slider of the optical system of NA ≧ 1. During reproduction, the formed magneto-optical film is focused, and during recording, light is transmitted as a near-field optical system by shifting the focal plane from the magneto-optical film by changing the incident angle of light. It is known that the light spot shape does not change even if the focal plane is shifted if the thickness is about 10 μm.

B. This is achieved by two-beam incidence. One beam sets the focus on the magneto-optical film, and the other beam allows the disk to be irradiated.

Next, a signal reproducing method using the above-mentioned floating magnetic head device will be described.

Here, a magnetic disk having a perpendicular magnetic film as a recording layer will be described as an example of a recording medium, but the recording medium may be a magnetic disk or a magneto-optical disk having an in-plane magnetic film as a recording layer. You may.

The magnetic disk, which is a recording medium, is rotated during recording and reproduction. The floating magnetic head device floats with the rotation of the magnetic disk.

In the case of the method of the present invention, the distance from the film surface is 10
When the thickness is 0 nm or more, the rise of the magnetic field at the position of the mark edge becomes gentle. In the case of ordinary magnetic heads for hard disks, magnetic shields are set on both sides of the head element to block the leakage magnetic field from the surroundings. Since the magnetic shield cannot be provided in the method of the present invention, the flying height is preferably set to 100 nm or less.

At the time of signal reproduction, a recording mark recorded on the perpendicular magnetic film 6 of the magnetic disk is transferred to the magneto-optical film 3 as shown in FIG.

In a magnetostatically coupled CAD, the magneto-optical film 3 having a rare earth element (RE) rich composition at room temperature is used.
However, as the temperature approaches the compensation temperature as the temperature rises, the magnetization decreases, and the state changes from the in-plane magnetization state to the perpendicular magnetization state.

By causing the magneto-optical film 3 and the perpendicular magnetic film 6 to face each other via a space (a space formed by floating of the magnetic head device) which is a non-magnetic intermediate layer, the temperature of the perpendicular magnetic film 6 is increased. Leakage magnetic field generated from the raised part,
The perpendicular magnetization existing only in the temperature-raised portion of the optical recording film 3 is magnetostatically coupled, and the magnetization state of the perpendicular magnetization film 6 is changed to the magneto-optical film 3.
A magneto-coupled CAD in which the data is transferred to and detected by the magnetic head is realized.

In a normal CAD used for a magneto-optical disk, the perpendicular magnetization film 6 has a compensating composition at room temperature, the magnetization increases as the temperature rises, and the leakage magnetic field generated from the recording layer has a maximum value near the reproduction temperature. Is shown. In the method of the present invention, the reproducing temperature of the recording layer is constant at room temperature and has magnetization at room temperature. In this case, although the reproduction characteristics are slightly deteriorated as compared with the normal CAD due to the influence of the leakage magnetic field of the surrounding recording marks, basically the same magnetic field is applied to the magneto-optical film 3.

The signal transferred to the photomagnetic film 3 has an NA
Read by the optical system of ≧ 1. At this time, by using a short-wavelength laser such as a blue laser as the laser light to be irradiated, it is possible to cope with higher recording density.

It is known that, for a short-wavelength light source, the Kerr rotation angle, which is the signal output of the magneto-optical disk, is smaller than that of a normal red laser. Methods for increasing the Kerr rotation angle include increasing the Co composition of TbFeCo,
Although there is a method such as mixing t, it cannot be applied to a normal magneto-optical disk because the Curie temperature increases and the magnetic anisotropy decreases.

Further, even with the same reproducing light intensity, the detection current of the detector has a limit of quantum efficiency, and the detection current of the blue laser decreases. To improve this, the reproduction light intensity for reproduction is increased. There is a need. However, when the reproducing light intensity is increased, a very large output is required as the recording light intensity in the ordinary magneto-optical recording, which imposes a burden on the laser.

In the method of the present invention, since no recording is performed on the magneto-optical film 3, there is no restriction on the Curie temperature, and a film having the largest Kerr rotation angle can be used. Specifically, TbFeCoPt or C
An o / Pt artificial lattice multilayer film or the like can be used.

Further, since it is not necessary to consider recording, it is easy to increase the intensity of the reproduction light. The use of a material having a high Curie temperature is advantageous in increasing the reproduction light intensity even thermally. Further, unlike an ordinary magneto-optical film in which heat is conducted to the recording layer, since an air layer having a low thermal conductivity exists between the magneto-optical film 3 and the perpendicular magnetic film 6, the heat of the magneto-optical film 3 is reduced by the perpendicular magnetization. It is hardly transmitted to the film 6, and the recording mark is not erased even if the intensity of the reproducing light is increased.

Finally, the present invention will be described based on specific experimental results.

First, the following magnetic films were formed on a glass substrate having a thickness of 1.2 mm.

Substrate / SiN (20 nm) / GdFeCo
(30 nm) / SiN (20 nm) of which GdFe
Co is a rare earth element (RE) -rich composition, and its composition is set so as to be an in-plane magnetic film at room temperature and a perpendicular magnetic film at a temperature of 150 ° C. or higher.

From the substrate side of this sample, NA = 0.55,
An optical system with a wavelength of 650 nm is incident, focused,
The reflected light was differentially detected.

An external magnetic field was applied thereto, and the reversal of the magnetization of the magnetic film was observed. FIG. 5 shows the results.

Here, the reproducing light intensity is 1.5 mW, the magnetic field intensity is 200 (Oe), and the modulation frequency is 2.5 MHz. In the figure, a waveform A is a coil current of an external magnetic field, and is proportional to the generated magnetic field. Waveform B is the RF output. High frequency noise is the noise that jumps into the RF detector,
It has nothing to do with the detected waveform.

According to this, it can be seen that the magnetization is modulated at a high speed following the external magnetic field, and a good output is obtained. Further, it was confirmed that the signal did not deteriorate even after being left for one hour in this state, and no deterioration of the magnetic film was observed even when the focus was continuously adjusted to the same position of the magnetic film. Further, when the modulation frequency of the magnetic field was changed, the RF amplitude was constant until the drive current of the magnetic head was reduced, and the waveform was almost the same as the drive current waveform.

Next, FIG. 6 shows the result of measuring the C / N by changing the intensity of the external magnetic field. According to this, the external magnetic field 90
It can be seen that C / N is not deteriorated to about (Oe). By improving the composition of the magnetic film, the magnetic field sensitivity can be further increased. When the magnetic field sensitivity is about 50 (Oe), the magnetic field can be easily sensed. It is possible.

On the other hand, the leakage magnetic field from the magnetic disk was calculated from the actual physical quantities actually used. FIG. 7 shows an example thereof.

In FIG. 7, the magnetic film is a perpendicular magnetization film having a thickness of 15 nm, a magnetization of 0.2 T, and a magnetic field when a cylindrical mark having a diameter of 200 nm is infinitely and uniformly magnetized. This is a distribution at a position 50 nm from the magnetic film (corresponding to the flying height). Vertical magnetic field Hz
The large offset is caused by a stray magnetic field because the mark is uniformly magnetized, and such an offset is eliminated if recording is performed appropriately. This amplitude is 100 (Oe) or more, which is sufficient to reverse the magnetization of the head on which the magnetic film is formed.

Next, the magnetic field distribution at the position of 100 nm is shown in FIG. According to this, although the external magnetic field was sufficient, it was found that the magnetic field distribution did not change sharply at the edge of the mark, and a good reproduction waveform could not be obtained. This is the same even if the magnetization of the magnetic film of the disk is increased, and it has been found that this detection method is essentially effective at a flying height of 100 nm or less.

In this example, the principle was confirmed with an optical system with NA = 0.55, but it goes without saying that the same operation is performed with an optical system with NA ≧ 1.

In the near-field optical system, the output from the end face of the flying head decreases due to the light interference and the evanescent wave. However, the head device according to the present invention can detect without loss.

Further, since this magnetic film responds to an external magnetic field only in a region smaller than the light spot size, super-resolution detection exceeding the spot size is possible. This is basically the same principle as CAD, which is one of the magnetic super-resolution methods. In the above experiment, the same result was obtained even if only the reproducing layer of CAD was formed. The major difference from CAD is that the reproducing layer moves with respect to the recording layer.

This experiment is equivalent to the case where the reproducing layer is moving at the same speed as the optical system. At this time, the magnetization is reversed at a high speed with respect to the external magnetic field. It is shown that the information of the layer is transferred to the reproducing layer (magneto-optical film).

[0062]

As is clear from the above description, in the present invention, a sufficient reproducing output can be obtained in a recording / reproducing system using a perpendicular magnetization film or an in-plane magnetization film, and the optical diffraction limit is obtained. Can be detected.

Further, according to the present invention, it is possible to eliminate the optical interference with the disk and the loss due to the evanescent wave peculiar to the near-field optical system, and to realize a stable optical system.

Furthermore, signal reproduction utilizing super-resolution can be performed, and signal reproduction excellent in transferability and high speed can be performed.

[Brief description of the drawings]

FIG. 1 is a side view schematically showing an example of a floating magnetic head device to which the present invention is applied.

FIG. 2 is a side view schematically showing another example of the floating magnetic head device to which the present invention is applied.

FIG. 3 is a side view schematically showing still another example of a floating magnetic head device to which the present invention is applied.

FIG. 4 is a schematic diagram illustrating a mechanism for transferring an information signal to a magneto-optical film.

FIG. 5 is a waveform diagram showing a state of reversal of magnetization of a magnetic film.

FIG. 6 is a characteristic diagram showing a change in C / N when an external magnetic field intensity is changed.

FIG. 7 is a characteristic diagram showing a magnetic field distribution of a leakage magnetic field from a magnetic disk, and is a characteristic diagram showing a magnetic field distribution at a position 50 nm from a magnetic film.

FIG. 8 is a characteristic diagram showing a magnetic field distribution at a position 100 nm from the magnetic film.

[Explanation of symbols]

1 slider, 2 solid immersion lens, 3
Magneto-optical film, 6 perpendicular magnetization film

Claims (9)

[Claims] 1. A flying magnetic head comprising: a flying slider provided with an optical system having a numerical aperture NA ≧ 1, and a magneto-optical film having a magneto-optical effect is formed at a focal position thereof. apparatus. 2. The magneto-optical film is an in-plane magnetized film at room temperature, exhibits magnetic field sensitivity to magnetization in a vertical direction by heating, and has one magnetic spot in an optical spot of the optical system having a numerical aperture NA ≧ 1. 2. The floating magnetic head according to claim 1, wherein only the portion is responsive to an external magnetic field. 3. The flying magnetic head according to claim 2, wherein said magneto-optical film is made of an alloy material containing at least Gd and a transition metal. 4. A flying magnetic head according to claim 1, wherein said magneto-optical film is a perpendicular magnetic film having soft magnetic characteristics. 5. A floating magnetic head according to claim 1, further comprising a focal position changing mechanism for shifting a focal position of the optical system having the numerical aperture NA ≧ 1 to a position outside the magneto-optical film. . 6. When reproducing an information signal of a magnetic disk on which a perpendicular magnetization film is formed, a flying slider is provided with an optical system having a numerical aperture NA ≧ 1, and has a magneto-optical effect at a focal position thereof. Using a floating magnetic head device having a magneto-optical film formed thereon, the magnetization of the perpendicular magnetic film is transferred to the magneto-optical film, and is read by an optical system having a numerical aperture NA ≧ 1, and is recorded on a magnetic disk. A signal reproducing method for reproducing a reproduced information signal. 7. A magneto-optical film, wherein the magneto-optical film is an in-plane magnetized film at room temperature and exhibits a magnetic field sensitivity to magnetization in a vertical direction by heating, and is applied to a magnetic disk by utilizing magnetic super-resolution. 7. The signal reproducing method according to claim 6, wherein the recorded information signal is reproduced. 8. The information recording apparatus according to claim 1, wherein the magneto-optical film is a perpendicular magnetization film having soft magnetic characteristics, and an information signal recorded on a magnetic disk is reproduced by setting a flying height of the flying magnetic head to 100 nm or less. Item 7. The signal reproducing method according to Item 6. 9. An optical system having a numerical aperture NA ≧ 1 is disposed on a flying slider when information signals are recorded / reproduced on / from a magnetic disk on which a perpendicular magnetization film is formed, and a magneto-optical device is provided at a focal position thereof. Using a floating type magnetic head device having a magneto-optical film having an effect formed thereon, the magnetization of the perpendicular magnetic film is transferred to the magneto-optical film, and is read by an optical system having a numerical aperture NA ≧ 1. By reproducing the information signal recorded on the disk and shifting the focal position of the optical system having the numerical aperture NA ≧ 1 to a position outside the magneto-optical film, light is directly transmitted from the optical system to the perpendicular magnetization film. A recording / reproducing method comprising irradiating and thermally recording an information signal.