JPH08180495A - Magnetic head - Google Patents

Abstract

PURPOSE: To stably reproduce signal magnetic field from a magnetic recording medium in spite of having a simple constitution using no polarization element related to a magnetic head using a magneto-optical effect. CONSTITUTION: A magnetic thin film 12 magnetically coupled with the magnetic recording medium 1 is formed on a transparent substrate 11, and on the other hand, this head is provided with a light source 20 for making a luminous flux 30 incident on the magnetic thin film 12 and a photodetector 23 receiving at least one side of the reflected light 31 or a transmitted light in the magnetic thin film 12 and generating an electric signal according to light quantity change. The head is provided with bias coils 50 generating the magnetic field larger than its coercive force for the magnetic thin film 12, and the incident surface of the luminous flux 30 from the light source 20 is set in nearly parallel to the direction of magnetization in the state where no magnetic thin film 12 is magnetically coupled with the magnetic recording medium 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head of a magnetic recording / reproducing apparatus, and more particularly to a reproducing head utilizing a magneto-optical effect.

[0002]

2. Description of the Related Art In recent years, there has been a great demand for higher density of magnetic recording and reproducing devices.

In the so-called induction type reproducing head which has been widely used in the past, the reproducing output depends on the track width or the relative speed to the magnetic recording medium, which is great for high density recording. It was a constraint.

Therefore, as a solution to this, a magnetic head using the magneto-optical effect has been proposed (for example,
(See Japanese Examined Patent Publication No. 56-33781).

A conventional magnetic head using the magneto-optical effect will be described below with reference to the drawings.

FIG. 5 is a block diagram of a conventional single pole type magnetic head using the magneto-optical effect. In FIG. 5, reference numeral 1 is a magnetic recording medium, and 11 is a substrate made of a transparent material which is in contact with the magnetic recording medium 1. On this transparent substrate 11, a magnetic thin film 12 made of permalloy is formed on an inclined surface 11c continuous to the surface 11a facing the magnetic recording medium 1, and a nonmagnetic reflective layer 15 is further formed thereon. The incident light 30 emitted from the light source 20 is reflected by the polarizer 2
After being linearly polarized by 1, the light is incident on the transparent substrate 11, is reflected by the inclined surface 11b in the transparent substrate 11, and is incident on the magnetic thin film 12. The reflected light 31 from the magnetic thin film 12 is the analyzer 2
After only the polarization component orthogonal to the incident light 30 is selected by 2, the photodetector 23 detects the intensity. That is, the polarizer 21 and the analyzer 22 have a so-called crossed Nicols relationship.

The conventional magnetic head using the magneto-optical effect constructed as described above operates as follows. First, the magnetic thin film 12 is applied by the magnetic field from the magnetic recording medium 1.
Is magnetized. The direction of magnetization is in the film plane (on the paper surface).
The polarization direction or ellipticity of the reflected light 31 slightly changes due to the interaction (longitudinal Kerr effect) between the magnetization of the magnetic thin film 12 and the incident light 30. Since the analyzer 22 separates and transmits only the polarization component in the direction orthogonal to the polarization direction of the incident light 30,
When the polarization plane is rotated or the ellipticity is changed, it is detected by the photodetector 23 as a change in the amount of light. By the above operation, the magnetization information recorded on the magnetic recording medium 1 is converted into a reproduction signal from the photodetector 23.

As described above, the reproducing head using the magneto-optical effect has the feature that the reproducing output does not depend on the track width or the relative speed to the magnetic recording medium in principle.

[0009]

However, the above-described conventional magnetic head has a problem that the structure of the optical system is complicated and expensive because the polarizing element is indispensable.

That is, the magnetic head having the conventional structure utilizes the "vertical Kerr effect" as a principle of operation to make the magnetic thin film 1
The change in magnetization of No. 2 was read out as a change in polarization. Therefore, some kind of polarizing element for detecting the change in polarization, such as converting the rotation of the plane of polarization into a change in the amount of light using the analyzer 22, is indispensable. As a result, there are problems that the configuration of the optical system becomes complicated and that the setting accuracy of the polarization plane of each element is required.

In addition, since the magnetic head having the conventional structure does not pay attention to the magnetic domain structure of the magnetic thin film 12, the reproduced waveform is unstable, and the magnetic signal from the magnetic recording medium 1 is small. In that case, there is a problem that the recording density cannot be improved because the output may not be obtained. This will be described in detail below.

That is, the above-described conventional magnetic head is based on the assumption that the magnetic thin film 12 is saturated by the magnetic field obtained from the magnetic recording medium 1. When the magnetic field from the magnetic recording medium 1 becomes larger than the coercive force, the magnetic thin film 12 is saturated upward (or downward). At this time, the magnetic thin film 12 has a single domain structure, and the output becomes stable.

However, during the transition from upward saturation to downward saturation (or vice versa), the magnetic thin film 12 has a multi-domain structure, and the change in magnetization is made by the movement of the domain wall.
As is well known, the domain wall movement is discontinuous due to impurities and defects in the thin film, and is characterized by no reproducibility. Therefore, the output on the way from the saturation to the reverse saturation becomes extremely unstable.

The magnetic field from the magnetic recording medium 1 decreases as the recording density increases. The maximum amount is the magnetic thin film 12
When the magnetic coercive force is smaller than the coercive force, the magnetic thin film 12 always operates in a multi-domain state, and the reproduction signal becomes extremely unstable. Especially, the movement of the domain wall becomes very small and the incident light 3
When the light no longer passes under the zero spot, the light always illuminates one magnetic domain. In that case, although the macroscopic magnetization of the magnetic thin film 12 changes with the magnetic field of the magnetic recording medium 1, the reproduction signal does not change at all. For the above reasons, it is difficult to achieve high density recording with the conventional magnetic head.

Further, since the magnetic head having the conventional structure has a so-called single pole type open magnetic circuit, the distribution of the magnetic flux density in the magnetic thin film 12 is maximized in the portion closest to the magnetic recording medium 1. The distribution is such that it decreases exponentially with increasing distance from the magnetic recording medium 1.
Therefore, in order to reproduce efficiently, the magnetic thin film 1
It was necessary to position the light spot at the end of the second magnetic recording medium 1 side, and high positioning accuracy was required. Further, since the magnetic thin film 12 is formed on the inclined surface, in order to reliably guide the input light to the magnetic thin film 12, the setting of the incident surface and the incident angle is greatly restricted. Moreover,
When the position of the light spot changes due to mechanical vibration or the like, the magnitude of the reproduction signal differs depending on the position of the change, which causes a problem that mechanical vibration is superimposed on the reproduction signal.

The present invention has been made in view of the above problems, and provides a highly sensitive magnetic head that has a simple structure and that converts a magnetization signal of a magnetic recording medium into an extremely stable and large electric signal. It is an object.

[0017]

In order to solve the above problems, a magnetic head according to a first aspect of the present invention has a magnetic thin film magnetically coupled to a magnetic recording medium formed on a transparent substrate. A magnetic head including a light source for making a light beam incident on the magnetic thin film, and a photodetector for receiving at least one of reflected light and transmitted light at the magnetic thin film and generating an electric signal according to a change in light quantity. In addition, a bias magnetic field generating means for applying a magnetic field larger than the coercive force to the magnetic thin film is provided near the magnetic thin film, and the magnetic thin film is magnetically coupled to the magnetic recording medium. The structure is such that the plane of incidence of the light flux from the light source is set substantially parallel to the direction of magnetization in the non-illuminated state.

According to a second aspect of the magnetic head of the present invention, there is provided a first magnetic core, a second magnetic core which comes into contact with the first magnetic core through a magnetic gap of a predetermined distance, and the first magnetic core. A closed magnetic circuit is formed by a magnetic thin film that connects the first magnetic core and the second magnetic core.

A magnetic head according to a third aspect of the present invention is the magnetic head according to the first or second aspect, wherein the magnetic thin film is provided substantially parallel to the running surface of the magnetic recording medium. ing.

A magnetic head according to a fourth aspect of the present invention is the magnetic head according to the second aspect, wherein the magnetic thin film is made of a material having good magneto-optical characteristics, and the first or second magnetic core has a high magnetic permeability. It has a constitution that it is made of a material.

[0021]

In the magnetic head of the first aspect, the magnetic thin film is forced to have a single domain structure. Therefore, the change of the magnetization of the magnetic thin film by the signal magnetic field from the magnetic recording medium is always performed only by the magnetization rotation under the condition of the single magnetic domain. Light is incident on the magnetic thin film from the light source so that the incident surface contains the magnetization vector in the absence of a magnetic field from the magnetic recording medium. The magnetization of a component perpendicular to the incident surface appears as an angle sine (sine component). The magnetization of the vertical component causes an interaction in the form of a “transverse Kerr effect” with respect to light, which changes the intensity of reflected light. Since the magnitude of the intensity change is proportional to the magnitude of the perpendicular component magnetization, it is substantially proportional to the magnitude of the magnetization rotation angle and further the magnitude of the signal magnetic field. By converting the intensity of the reflected light into an electric signal corresponding thereto by the photodetector, the magnetization signal of the magnetic recording medium is converted into an electric signal corresponding thereto. The above operation is not affected by whether or not the signal magnetic field is larger than the coercive force of the magnetic thin film, so that signal reproduction is surely performed even during high density recording. Further, by utilizing the transverse Kerr effect, the polarizing element as in the conventional example is not needed at all, and the optical system becomes extremely simple.

Further, in the magnetic head of claim 2,
A closed magnetic circuit is formed by providing the first and second magnetic cores. Therefore, the magnetic resistance is reduced, the reproduction efficiency is increased, and the magnetic flux density in the magnetic thin film is uniform at all positions. Therefore, the magnetization rotation angle of the magnetic thin film becomes uniform. Therefore, even if the position of the incident light on the magnetic thin film changes due to mechanical vibration or the like, it does not affect the reproduction signal (this means that
This also applies when using the vertical car effect as well as when using the horizontal car effect).

Further, in the magnetic head of claim 3,
By providing the magnetic thin film substantially parallel to the running surface of the magnetic recording medium, it becomes easy for the light flux to enter the magnetic thin film and for the reflected light to be received. Further, there is no restriction on the setting of the incident surface and the incident angle, and the light beam can be incident on the magnetic thin film under the optimum conditions.

Further, in the magnetic head of the fourth aspect, the magnetic thin film is made of a material having a good magneto-optical characteristic among the elements forming the closed magnetic path, and the first or second magnetic core is made of a highly transparent material. Since it is made of a magnetic material, both improvement of magneto-optical conversion efficiency and improvement of magnetic efficiency are achieved. Therefore, signal reproduction with higher sensitivity is performed.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic head (a reproducing head utilizing the magneto-optical effect) according to an embodiment of the present invention will be described below with reference to the drawings. 1 is a front view of a magnetic head according to an embodiment of the present invention, FIG. 2 is a side view thereof, and FIG.
FIG.

In FIGS. 1 to 3, reference numeral 11 denotes a transparent substrate made of a high-refractive-index dielectric material, which is made of optical glass SF11 (refractive index 1.78). The transparent substrate 11 is cut out in a trapezoidal column shape, and the magnetic thin film 12 is formed on the bottom surface 11a sandwiching the inclined surfaces 11b and 11c. The magnetic thin film 12 is formed by vapor-depositing a ternary alloy of 45% iron, 20% cobalt, and 35% nickel to a thickness of 20 nm under the condition of 5 × 10 ⁻⁵ mmHg.

Reference numerals 41 and 42 respectively denote a first magnetic core and a second magnetic core, which are in contact with each other with a magnetic gap 43 interposed therebetween. The first magnetic core 41 and the second magnetic core 42 are connected to the peripheral portion of the magnetic thin film 12 at their end faces opposite to the magnetic gap 43. Further, a cover layer 14 made of a low refractive index dielectric material is laminated on the central portion of the magnetic thin film 12.

The first magnetic core 41 and the second magnetic core 42
Is composed of so-called permalloy of 19% of iron and 81% of nickel, and has a large magnetic permeability and excellent soft magnetism as compared with the ternary alloy of 45% of iron, 20% of cobalt and 35% of nickel of the magnetic thin film 12. Further, the cover layer 14 is made of silicon dioxide and has a thickness sufficiently thicker than a wavelength (680 nm) of a light source to be described later to prevent escape of incident light and is laminated by about 2 μm.

A closed magnetic circuit 45 is formed by the first magnetic core 41, the magnetic thin film 12 and the second magnetic core 42, and the magnetic gap 43 faces the magnetic recording medium 1 with a slight spacing. are doing. The magnetic thin film 12 is substantially parallel to the running surface of the magnetic recording medium 1.

Information is written on the magnetic recording medium 1 as magnetization 2 alternating with a recording head (not shown).

Numerals 50 and 50 are a pair of bias coils (not shown in FIG. 2) for applying a bias magnetic field Hb to the magnetic thin film 12 in a direction substantially orthogonal to the magnetic path 45 therein. The magnitude of the bias magnetic field Hb is about 10
It is Oersted, and is set sufficiently larger than the coercive force of the magnetic thin film 12 of about 4 Oersted. Therefore, the magnetic thin film 12 always has a single domain structure, and has a magnetization vector in the direction indicated by the arrow M ₀ in FIG. 3 when there is no magnetic flux from the magnetic recording medium 1.

A light source 20 emits linearly polarized incident light 30, which is a laser diode (wavelength 680 nm,
It has an output of 1 mW) and a condenser lens (both not shown). The incident light 30 vertically enters the transparent substrate 11, is reflected by the inclined surface 11b, and then enters the magnetic thin film 12.

The reflected light 31 from the magnetic thin film 12 is reflected by the inclined surface 11c, then vertically emitted from the transparent substrate 11 and incident on the photodetector 23. The photodetector 23 includes a photodiode, which converts the reflected light 31 into an electric signal according to the amount of light.

The plane of incidence on the magnetic thin film 12, that is, the plane formed by the incident light 30 and the reflected light 31 is in the plane of the paper of FIG. 1, and the above-mentioned arrow M ₀ is also included in that plane. The incident angle θ on the magnetic thin film 12 is 58 degrees, and the critical angle (56.2 degrees) determined by the transparent substrate 11 and the cover layer 14.
Is set to about 3% larger than.

The plane of polarization of the incident light 30 is set to P polarization.

The operation of the magnetic head of this embodiment having the above structure will be described below.

When the magnetic recording medium 1 is run in the lateral direction along the plane of the drawing in FIG. 2, the alternating signal magnetic field generated from the magnetization 2 of the magnetic recording medium 1 becomes first based on the same principle as that of a general ring type head. It is guided to the first and second magnetic cores 41 and 42 and applied to the magnetic thin film 12. In the conventional example shown in FIG. 5, the magnetic flux density in the magnetic thin film exponentially decreases with distance from the magnetic recording medium, because the open magnetic circuit of a so-called single pole type is used. In the embodiment, since the closed magnetic circuit 45 is formed, the magnetic flux density in the magnetic thin film 12 is uniform throughout.

Since the magnetic thin film 12 is made into a single magnetic domain as described above, the state of magnetization with respect to the applied magnetic field is uniquely determined as the magnetization rotation angle, and the direction of the magnetization 2 on the magnetic recording medium 1 is made positive or negative. Correspondingly, magnetization rotation occurs as shown by arrows + M and -M in FIG. As described above, since a uniform magnetic field is applied to the magnetic thin film 12, the magnetization rotation angle in the magnetic thin film 12 is the same in all parts.

When the rotation of the magnetization vector occurs, a magnetization component perpendicular to the light incident surface appears. That is, in FIG.
For example, if the magnetization vector rotates from M ₀ by Φ, M
_A vertical component occurs by ₀ sin Φ. The magnetization component perpendicular to the incident surface causes an interaction called “transverse Kerr effect” with respect to light, and gives a perturbation to the change in the light amount of the reflected light 31. Photodetector 2
The light is received by 3 and converted into an electric signal according to the amount of light.

FIG. 4 is a characteristic diagram showing the relationship between the direction of the magnetization vector and the amount of detected light in this embodiment. In FIG. 4, the horizontal axis is the direction Φ of the magnetization vector, and the clockwise direction is positive with respect to the direction indicated by the arrow M ₀ in FIG. The vertical axis represents the amount of light detected by the photodetector 23, and is based on the case where the orientation Φ of the magnetization vector is 0 degree.

From FIG. 4, the detected light quantity is the direction Φ of the magnetization vector.
It can be seen that the sinusoidal continuous function has a maximum at −90 degrees and a minimum at 90 degrees. 9
In the states of 0 degree and -90 degrees, the magnetization vector is the closed magnetic path 4
5, that is, a state orthogonal to the incident light 30. Since the magnetic thin film 12 always operates as a single magnetic domain as described above, the magnetization state is uniquely determined as the rotation of the magnetization vector. As can be seen from FIG. 4, since a continuous output is obtained with respect to the magnetization rotation angle, it is possible to always obtain a stable and continuous reproduction signal. Also,
That is true regardless of the magnitude of the signal magnetic field.

Further, in this embodiment, even when the signal magnetic field becomes small during high-density recording, that is, even when the change amount of the magnetization of the magnetic thin film 12 becomes small, it can be reliably extracted as the maximum light amount change. Is. In FIG. 4, the slope of the graph represents the efficiency of converting a change in the magnetic field into a change in the amount of light. That is, when the magnetization rotation changes in the range of the saturation magnetization or less, the larger the gradient of the graph is, the larger the change of the light amount can be obtained. The maximum inclination from FIG. 4 is when the magnetization direction Φ is 0 degrees or 180 degrees, that is, when the magnetization is parallel to the direction of the incident light 30. As described above, in this embodiment, by the bias coils 50, 50, the spontaneous magnetization of the magnetic thin film 12 in the state where there is no magnetic field from the magnetic recording medium 1 is in the traveling direction of light as shown by the arrow M ₀ in FIG. It is set to be parallel. Therefore, the maximum detected light amount ΔI can be obtained with respect to the rotation angle ΔΦ of the spontaneous magnetization. As a result, signal reproduction during high density recording can be performed more reliably.

Further, as described above, in the present embodiment, since the magnetization rotation angles of the magnetic thin film 12 are equal to each other, the incident light 30 on the magnetic thin film 12 is caused by, for example, mechanical vibration.
Even if the position of is changed, if it is in the magnetic thin film 12, it does not affect the reproduction signal.

In this embodiment, the magnetic thin film 12 is made of iron.
While being formed of a cobalt-nickel ternary alloy, the first,
Since the second magnetic cores 41 and 42 are made of permalloy, it is possible to realize reproduction with higher sensitivity. When selecting a material for the purpose of improving reproduction sensitivity, two directions can be considered. One is to use a material that converts the magnetization rotation of the magnetic material into a larger change in the amount of light, that is, a material having a large magneto-optical effect. The other is to use a material having a small magnetic resistance, that is, a material having a large magnetic permeability so as to efficiently absorb the magnetic flux from the magnetic recording medium 1. The present inventors have conducted experiments to find iron-cobalt-
We have found a material showing a large magneto-optical effect among the ternary alloys of nickel. It is well known that permalloy is a good soft magnetic material having a large magnetic permeability. Therefore, in the present embodiment, the magnetic thin film 12 in which the interaction between light and magnetism is performed.
Is formed of a ternary alloy of iron-cobalt-nickel having a large magneto-optical effect, and the first and second magnetic cores 41 and 42, which are not required to have magneto-optical properties, are formed of permalloy having a high magnetic permeability, thereby achieving high magnetic properties. A structure has been realized that satisfies both the requirements of optical conversion efficiency and high magnetic efficiency. Therefore, reproduction with higher sensitivity is possible.

In this embodiment, the reflected light 31 from the magnetic thin film 12 is detected, but the transmitted light may be detected. However, in that case, since the magnetization rotation of the magnetic thin film occurs in the plane, it is necessary to make the incident light incident on the magnetic thin film at a predetermined angle other than perpendicular, and it is particularly preferable to set it near the critical angle. Further, it may be configured to detect both reflected light and transmitted light.

Further, in this embodiment, the magnetic thin film 12 and the cover layer 14 which is a low refractive index dielectric are sequentially laminated on the transparent substrate 11 which is a high refractive index dielectric. The present invention is not limited to this, and may be applied to any structure as long as the magneto-optical material and light interact with each other. Above all, the present inventors have found that extremely high modulation can be obtained by the configuration shown below. That is, a transparent substrate that is a high-refractive-index dielectric, a low-refractive-index dielectric thin film, a noble metal thin film, a magnetic metal thin film, and a low-refractive-index dielectric layer are laminated in this order (more specifically, high-refractive-index glass (refractive index 1.87) / silicon dioxide (film thickness 270 nm) / silver (film thickness 20 nm) / iron (film thickness 20 nm) / silicon dioxide (film thickness 2)
By forming a multi-layered film of 000 nm) and positively utilizing plasmon resonance, a modulation rate that is an order of magnitude higher than the general transverse Kerr effect of several tens of percent was obtained. By adopting such a configuration, the present invention can be made more effective.

Further, in the present embodiment, the magnetic thin film 12 is made into a single magnetic domain by using the bias coils 50 and 50 to generate a magnetic field. However, the present invention is not limited to this. Any device that has a means for forming a single magnetic domain may be used. For example, the structure using the remanent magnetization of the ferromagnetic material or the structure using the exchange interaction of the antiferromagnetic film may be used.

[0048]

The present invention has the following effects.

(1) According to the magnetic head of claim 1, a bias magnetic field generating means for applying a magnetic field larger than the coercive force to the magnetic thin film is provided, and the magnetic head is magnetically coupled to the magnetic recording medium. By setting the plane of incidence of the light flux from the light source almost parallel to the direction of magnetization in the non-exposed state, high-density magnetic recording can be read with high sensitivity and stability, even with a simple configuration. it can. That is, by utilizing the lateral Kerr effect, a polarizing element as in the prior art is not needed at all, and the optical system becomes extremely simple. Further, by always operating the magnetic thin film in the state of a single magnetic domain, it is possible to always obtain a stable reproduced signal even at the time of high-density recording in which the signal magnetic field becomes fine.

(2) According to another aspect of the magnetic head of the present invention, the first magnetic core, the second magnetic core that comes into contact with the first magnetic core through a magnetic gap of a predetermined distance, and the first magnetic core are provided.
Since a closed magnetic circuit is formed by providing the magnetic core and the magnetic thin film that connects the second magnetic core with each other, the magnetic resistance is reduced, reproduction efficiency is improved, and the magnetization rotation angle in the magnetic thin film is increased at all positions. It can be uniform. Therefore, even if the position of the incident light on the magnetic thin film changes due to mechanical vibration or the like, it does not affect the reproduction signal, and a highly efficient and stable reproduction signal is obtained. It is possible (this is true whether the horizontal Kerr effect or the vertical Kerr effect is used).

(3) According to the magnetic head of claim 3, the magnetic thin film is provided substantially parallel to the running surface of the magnetic recording medium, so that the light flux can be easily incident on the magnetic thin film and the reflected light can be easily received. Can be converted. Further, there is no restriction on the setting of the incident surface and the incident angle, and the light beam can be incident on the magnetic thin film under the optimum conditions.

(4) According to the magnetic head of claim 4, among the elements forming the closed magnetic path, the magnetic thin film is made of a material having excellent magneto-optical characteristics, and the first or second magnetic core is formed. Since it is made of a material having a high magnetic permeability, both improvement of magneto-optical conversion efficiency and improvement of magnetic efficiency can be achieved. Therefore, signal reproduction with higher sensitivity can be performed.

[Brief description of drawings]

FIG. 1 is a front view of a magnetic head according to an embodiment of the present invention.

FIG. 2 is a side view of the magnetic head of the embodiment.

FIG. 3 is a sectional view taken along line AA in FIG. 2;

FIG. 4 is a characteristic diagram showing the relationship between the direction of magnetization and the amount of detected light in this embodiment.

FIG. 5 is a configuration diagram of a conventional magnetic head using a magneto-optical effect.

[Explanation of symbols]

 1 ... Magnetic recording medium 2 ... Magnetization 11 ... Transparent substrate 12 ... Magnetic thin film 14 ... Cover layer 20 ... Light source 23 ... Photodetector 30 ... Incident light 31 ... Reflected light 41 ... First Magnetic core 42 ... second magnetic core 43 ... magnetic gap 45 ... closed magnetic path 50 ... bias coil (bias magnetic field generating means) Hb ... bias magnetic field

Claims (4)

[Claims] 1. A magnetic thin film magnetically coupled to a magnetic recording medium is formed on a transparent substrate, a light source for injecting a light flux to the magnetic thin film, and reflected light or transmitted light from the magnetic thin film. A magnetic head having a photodetector for receiving at least one of the above and generating an electrical signal according to a change in light quantity, wherein a magnetic field larger than the coercive force of the magnetic thin film is provided in the vicinity of the magnetic thin film. Bias magnetic field generating means for applying is provided, and the incident surface of the light flux from the light source is substantially parallel to the direction of magnetization of the magnetic thin film in a state not magnetically coupled to the magnetic recording medium. A magnetic head characterized by being set. 2. A first magnetic core, a second magnetic core that abuts the first magnetic core via a magnetic gap of a predetermined distance, the first magnetic core and the second magnetic core. A magnetic head characterized in that a closed magnetic circuit is formed by a magnetic thin film that connects the magnetic heads. 3. A magnetic thin film is provided substantially parallel to the running surface of the magnetic recording medium.
Alternatively, the magnetic head according to claim 2. 4. The magnetic material according to claim 2, wherein the magnetic thin film is made of a material having good magneto-optical characteristics, and the first or second magnetic core is made of a material having high magnetic permeability. head.