JP4584417B2 - Magnetic information reproducing probe and method of manufacturing the probe - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic information reproducing probe and a method for manufacturing the probe, and more particularly, to a magnetic information reproducing probe in which a magnetic head used for reproducing optically assisted magnetic recording and a heat source are integrated, and a method for manufacturing the probe. Is.
[0002]
[Prior art]
As a new magnetic information recording method, for example, there is an optically assisted magnetic information recording method for increasing the density by utilizing the characteristics at the compensation temperature of a ferrimagnetic material as disclosed in Japanese Patent Laid-Open No. 4-176034. This is a method for recording and reproducing by using a ferrimagnetic material such as TbFeCo having a magnetic compensation point temperature near room temperature as shown in FIG. 14 and heating the recording layer by laser light irradiation as shown in FIG. In this method, when a recording magnetic field is applied to the recording layer by the recording head 13 and the laser beam is irradiated, the temperature of the irradiated portion 12 increases and the coercive force 10 decreases, and the magnetization direction depends on the recording magnetic field. Recording is performed with easy change. However, since the coercive force 10 remains high in the non-irradiated portion, the magnetization direction does not change and recording is not performed. Therefore, magnetic information can be selectively recorded only on the irradiated portion 12 regardless of the width of the head.
[0003]
Further, when the reproducing area is irradiated with the laser beam while the reproducing head 13 is operated, the temperature of the irradiated portion 12 is increased and the residual magnetization 11 is increased, so that the recorded information can be easily detected. Since the temperature is not increased and the residual magnetization 11 remains low in the unirradiated portion, no signal is read out even if there is recorded information. Therefore, magnetic information can be selectively reproduced only in the irradiated portion 12 regardless of the width of the head.
[0004]
As described above, since only the portion irradiated with the laser beam can be recorded and reproduced, magnetic recording with a track width narrower than the magnetic head width determined by the temperature rise area width corresponding to the laser beam diameter becomes possible. .
[0005]
[Problems to be solved by the invention]
In a conventionally proposed optically assisted magnetic information recording system, the optical head (pickup) is separated from the magnetic head and located on the opposite side of the recording medium, and the position of the magnetic head in the in-plane direction of the recording medium is set. It was difficult to match. Further, since it is impossible to use both sides of the recording medium, it has been a problem in increasing the recording capacity. Furthermore, in order to minimize the temperature rise of the recording medium, the distance between the temperature rising area on the recording medium and the magnetic field application area or the magnetic field detection area is made as small as possible so that no alignment is required and both sides of the recording medium are used. There has been a demand for a method that enables the temperature rise to be minimized.
[0006]
As a method therefor, there is a combination of a magnetic head and an optical head, and some have been proposed in the fields of magneto-optical recording and thermomagnetic recording. For example, there is a magneto-optical pickup in which a laser and an optical system are incorporated in a magnetic circuit having a gap as disclosed in Japanese Patent Application Laid-Open No. 1-273252. This is intended to make it possible to realize an ideal composite head by incorporating the laser light emitting portion and the magnetic head gap by incorporating them in the gap. However, in recent years, magnetic circuits corresponding to high-density recording have such voids, and since a laminated thin film head is used, it is not widely used.
[0007]
The present invention has been made to overcome such problems. Specifically, the relative positional relationship between the position irradiated with the laser beam for raising the temperature and the position of the magnetic head on the surface of the recording medium is changed. One of the main objectives is to provide no probe type head.
[0008]
[Means for Solving the Problems]
According to the present invention, a laser beam is supplied to a recording medium, having a core and a clad, and having a conical sharp portion formed at one end of the core so as to protrude from an end face of the clad. An optical fiber for detecting the magnetic field, a magnetic field detecting element for detecting the magnetic field of the recording medium formed on the end surface of one end of the cladding of the optical fiber, and the magnetic field detecting film formed on the side surface of the optical fiber. Provided is a magnetic information reproducing probe including a thin film electrode for an element.
[0009]
That is, in the present invention, a magnetic field detection element, that is, a magnetic head is formed on a sharpened end face of an optical fiber as a probe, and a recording medium is heated by passing laser light through the probe, and at the same time, magnetic information is reproduced by the magnetic head. It is characterized by performing.
When this probe is used for optically assisted magnetic recording, since the optical fiber and magnetic head are integrated, the position of the laser beam and the position of the magnetic head are constant and within the probe diameter, thereby accurately Reproducible magnetic information can be reproduced.
[0010]
In the present invention, a magnetic field detection element is formed on the sharpened end face of the optical fiber.
The magnetic field detecting element is composed of an insulating semiconductor compound layer and at least two ferromagnetic layers sandwiching the semiconductor compound layer, and a current flowing through the semiconductor compound layer is used as a magnetization direction of the two ferromagnetic layers. A “magnetic tunnel junction element” that can exhibit a so-called “tunnel type giant magnetoresistance effect” that can be changed by the above-mentioned is preferable.
[0011]
Here, one of the two ferromagnetic layers is composed of a non-magnetic metal layer portion and two ferromagnetic layer portions separated by the non-magnetic metal portion and coupled antiferromagnetically, and the other ferromagnetic layer. The body layer is preferably composed of one layer or multiple layers of ferromagnetic layers. For the ferromagnetic layer portion, Fe, Co, Ni, or an alloy thereof can be used.
Also, it is preferable that one of the two ferromagnetic layer portions is in contact with an alloy containing Mn, for example, an antiferromagnetic layer made of FeMn, because an effect of imparting unidirectional anisotropy can be obtained by exchange interaction. .
[0012]
Specifically, the insulating semiconductor compound layer can employ a compound layer of any one of Al and Si and any of B, C, N, O, P, and S. As the nonmagnetic metal layer, Cu, Ag, or Au layers can be employed.
Another example of the magnetic field detection element is a so-called “giant” which is configured by alternately laminating magnetic layers and conductor layers, and can change the current flowing through the conductor layers depending on the magnetization direction of the magnetic layer. It is also possible to use an “artificial lattice magnetic film” that can exhibit a “magnetoresistance effect”.
Here, the magnetic layer is a layer of Fe, Co, Ni, or a compound thereof, and the conductor layer is a layer of Cu, Ag, or Au.
[0013]
On the other hand, the magnetic information reproducing probe according to the present invention includes a thin film electrode for the magnetic field detecting element described above on the side surface of the optical fiber. Specifically, this thin film electrode is formed of a Cu, Ag or Au film having a film thickness of 1 to 5 μm by a method usually employed for electrode formation in this field, such as sputtering, thermal evaporation, or plating. Can be obtained.
[0014]
According to another aspect of the present invention, one end of an optical fiber having a core and a clad is etched to remove one end of the clad and protrude from the end face of the etched clad. A first step of projecting and forming a conical sharpened portion at one end of the core ; a second step of covering the sharpened portion of the optical fiber after the first step, the end face and the side surface of the clad with a thin film for a lower electrode; and a sharpened optical fiber A third step of covering the thin film for the lower electrode covered on the end face of the portion and the clad with a multilayer thin film; and laminating an insulator layer on the thin film for the lower electrode covered on the multilayer thin film and the side surface of the optical fiber A fourth step of removing; the fifth step of removing the insulator layer covered by the multilayer thin film within a concentric circle having a radius smaller than the radius of the optical fiber; A sixth step of covering the multilayer thin film and the insulating layer with the thin film for the upper electrode; and the thin film for the lower electrode, the insulating layer and the thin film for the upper electrode laminated on the side surface of the optical fiber along the long axis of the optical fiber. A seventh step of removing one strip-like portion, and an eighth step of removing the thin film for the lower electrode, the multilayer thin film and the thin film for the upper electrode laminated on the tip portion of the sharpened portion of the optical fiber; a ninth step of removing a portion of the thin film for the upper electrode to expose the insulating layer; by isosamples removing a portion of the exposed the insulating layer to expose the said thin film for the lower electrode, the recording An optical fiber having the conical sharpened portion for supplying laser light to the medium, and a magnetic field detecting element formed on the end face of one end of the clad of the optical fiber for detecting the magnetic field of the recording medium; Upper and lower power on the side of the optical fiber It can provide a manufacturing method of a magnetic information reproducing probe comprising: a tenth step to obtain a magnetic information reproducing probe provided with a thin film electrode for said magnetic field detecting element formed as use thin film.
Here, as the etching process in the first step, a selective chemical etching using a mixed aqueous solution of NH ₄ F and HF is preferable.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on the embodiments shown in FIGS.
FIG. 1 is a diagram showing an outline of an optically assisted magnetic recording system using a magnetic information reproducing probe according to the present invention.
[0017]
In FIG. 1, a magnetic information reproducing probe 1 includes an optical fiber 2, a magnetic field detection element 14 formed on the sharpened end face of the optical fiber, and a thin film electrode 15 formed on a side surface of the optical fiber 2. And mainly.
The optical fiber 2 includes a core 1b constituting a central portion and a clad 1a around the core 1b. The core 1b at the end face is sharpened in a conical shape (sharp part: 2a), and the clad 1a around the core 1b is removed. ing.
[0018]
The magnetic field detection element 14 is composed of a multilayer thin film 9 described later, and constitutes a so-called magnetic head.
The thin film electrode 15 includes an upper electrode (layer) 5 and a lower electrode (layer) 3 that are electrically connected to the multilayer thin film 9. In addition, 4 is an insulating layer of both electrodes (layers) 3 and 5, and 6 and 6 are conducting wires of both electrodes (layers) 3 and 5.
[0019]
Thus, the probe sharpened portion 2a is brought close to the recording medium 8 by means not shown, and the recording medium 8 is heated on the recording medium 8 through the laser beam 7 and recorded on the recording medium 8 by the multilayer thin film 9 of the magnetic head deposited on the probe end face. The magnetic information is reproduced. Reference numeral 16 denotes a laser for supplying laser light to the optical fiber 2, and reference numeral 17 denotes a support portion (means) for supporting the recording medium 8 so as to be movable.
[0020]
Next, a manufacturing method of the probe shown in FIG. 1 will be described in detail with reference to FIGS.
FIG. 2 is a flowchart showing the overall flow of the process. 3 to 13 are process explanatory views for explaining a probe manufacturing process. FIG. 3A is a side view of the optical fiber, and FIG. 3B is a state of the end face of the optical fiber.
[0021]
First, in FIG. 2, the manufacturing method of the probe for reproducing magnetic information consists of the following steps (1 to 10). That is,
(1) Sharpening the tip of the optical fiber (first step)
(2) Depositing the lower electrode layer on the optical fiber (second step)
(3) Depositing a magnetic head thin film on the tip of the optical fiber (third step) (4) Depositing an insulating layer on the optical fiber (fourth step)
(5) Partial etching of the insulating layer on the end face of the optical fiber (fifth step) (6) Deposition of the upper electrode tank on the optical fiber (sixth step)
(7) Etching leaving part of the film deposited on the side of the optical fiber (seventh step)
(8) Etching around the core at the end face of the optical fiber (eighth step)
(9) The insulating film is exposed by partially etching the film remaining on the side surface of the optical fiber (9th step)
(10) The insulating film exposed on the side surface of the optical fiber is partially etched to expose the lower electrode tank (tenth step).
[0022]
Next, in the first step shown in FIG. 3, the tip of the optical fiber is sharpened. For this purpose, for example, selective chemical etching using a mixed aqueous solution of NH ₄ F and HF as described in “Motoichi Otsu: Applied Physics Vol. 65 No. 1,“ Photon Scanning Tunneling Microscope Technology ”” is used. That is, when the tip portion S of the optical fiber is immersed in a mixed aqueous solution of NH ₄ F and HF having the same volume ratio of HF and H ₂ O for about 1 hour, the light shown by the broken line in FIG. The core 1b (material: quartz (high refractive index)), which is the central portion of the fiber, is selectively sharpened, and the end face of the surrounding cladding 1a (material: quartz (low refractive index)) is removed. When the volume ratio of NH ₄ F to HF exceeds 5 times in this aqueous solution, the tip angle of the core 1b is determined not by the volume ratio but by the concentration of GeO _{2 in} the core 1b.
[0023]
Next, in the second step shown in FIG. 4, a thin film for an electrode having a thickness (for example, 1 to 5 μm) sufficient for conduction on the sharpened end face (including the sharpened portion 2a) and side face of the optical fiber. Is deposited by sputtering. This becomes the lower electrode layer 3 of the magnetic head, and typical materials include Cu, Ag, Au, and the like. In this embodiment, the sputtering method is used as the deposition method, but other deposition methods such as a thermal evaporation method and a plating method may be used.
[0024]
Next, in a third step shown in FIG. 5, a multilayer thin film 9 constituting a head for detecting a magnetic field is deposited by sputtering on the sharpened end face of the optical fiber.
As a principle for detecting a magnetic field, the magnetoresistive effect has generally been used, and in recent years, the giant magnetoresistive effect having higher detection sensitivity has begun to be used. In this embodiment, a tunnel type giant magnetoresistive effect (tunnel magnetoresistive effect) with higher detection sensitivity is used, and a multilayer including a ferromagnetic layer / insulating semiconductor compound layer / ferromagnetic layer is used as a structure for realizing it. A thin film structure is adopted, and for example, a NiFe / Co / Al ₂ O ₃ / Co film (film thickness: 17/5/5/75 nm) is adopted as the multilayer thin film 9.
[0025]
Next, in a fourth step shown in FIG. 6, the insulating layer 4 is deposited by sputtering on the sharpened end face and side face of the optical fiber. This is to insulate the lower electrode layer 3 deposited in the second step from the upper electrode layer 5 deposited in the subsequent sixth step. A typical material is Al ₂ O ₃ or the like, and the thickness required for insulation varies depending on the material used and the applied voltage. For example, when the material is Al ₂ O ₃ and the applied voltage is 1 V, the required film thickness is 0.1 μm.
[0026]
Next, in the fifth step shown in FIG. 7, only the insulating layer 4 among the layers deposited on the sharpened end face of the optical fiber is subjected to ion beam etching in a concentric circle range having a radius smaller than the radius of the optical fiber. Etching is performed by anisotropic dry etching such as the following (the same applies to the following etching). This is a process for conducting the magnetic head film 9 and the upper electrode layer 5, but the fact that the entire end face is not etched prevents the lower electrode layer 3 and the upper electrode layer 5 from contacting each other at the edge of the end face. Because. Although the etching range depends on the etching accuracy, 70 to 95% of the end face of the optical fiber is preferable, and approximately 90% is the limit.
[0027]
Next, in a sixth step shown in FIG. 8, an upper electrode layer 5 having a thickness (for example, 1 to 5 μm) necessary for conduction is deposited by the same material and method (sputtering method) as those in the second step.
Here, the magnetic head film 9 deposited on the end face of the optical fiber in the third step needs to be as close to the optically assisted magnetic recording medium as possible in order to increase the acting force at the time of reproducing magnetic information. Three conditions necessary for this are shown below.
-The lower electrode layer 3 deposited in the second step is made as thick as possible.
The insulating layer 4 deposited in the fourth step and the upper electrode layer 5 deposited in the sixth step are made as thin as possible.
The thickness of the film deposited on the end face of the optical fiber at the end of the sixth step is within a range thinner than the height of the probe sharpened portion 2a from the end face, and is as close as possible to that height.
[0028]
Next, in a seventh step shown in FIG. 9, all the layers deposited on the side surfaces of the optical fiber are etched by anisotropic dry etching. However, the etching direction is inclined in the major axis direction by X ° (0 <X <90) from the direction perpendicular to the side surface so as not to etch the layer deposited on the end face of the optical fiber. This angle X varies depending on the anisotropy of the etching used. If the anisotropy is large, X may be small, and if the anisotropy is small, X must be large. Further, while fixing one of the optical fiber and the etching direction, the etching is performed while rotating the other, and the etching is performed when the layer 5 has a necessary width as an electrode as shown in FIG. finish.
[0029]
Next, in the eighth step shown in FIG. 11, all the layers deposited on the end face are etched in a concentric range as small as possible centered on the tip of the optical fiber, that is, in a concentric range having a radius of minimum resolution of etching. To do.
[0030]
Next, in the ninth step shown in FIG. 12, among the layers remaining on the side surface of the optical fiber, the upper electrode layer 5 is about 1 mm (length) in the major axis direction and about the diameter of the optical fiber in the minor axis direction ( The insulating layer 4 deposited in the fourth step is exposed.
[0031]
Next, in the tenth step shown in FIG. 13, the insulating layer 4 in the range etched in the ninth step is further about 0.5 mm (length, exposed) in the major axis direction so as to have a sufficient width as an electrode portion. Etching is performed in a range that is 1/2 of the insulating layer 4) and about the diameter of the optical fiber in the minor axis direction (width, the same width as the exposed insulating layer 4) to expose the lower electrode layer 3 deposited in the sixth step.
[0032]
In order to incorporate the fabricated probe into the optically assisted magnetic recording / reproducing system, the conventional reproducing magnetic head and optical pickup are replaced, that is, the wiring connected to the reproducing magnetic head as shown in FIG. It is only necessary to connect the upper electrode layer 5 and the lower electrode layer 3 on the side surface, and connect the end of the probe that is not sharpened to the laser 16 (light source).
[0033]
【The invention's effect】
According to the present invention, accurate magnetic information can be reproduced in the optically assisted magnetic recording system, and accordingly, the interval between magnetic information necessary for stable reproduction can be reduced. Can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of an optically assisted magnetic system using a probe produced in the present invention.
FIG. 2 is a flowchart of a probe manufacturing process.
FIG. 3 is a diagram showing a process of sharpening the tip of an optical fiber.
FIG. 4 is a diagram showing a process of depositing a lower electrode layer 3;
FIG. 5 is a diagram showing a process of depositing a multilayer thin film 9 for a magnetic head.
FIG. 6 is a diagram illustrating a process of depositing an insulating layer 4;
FIG. 7 is a diagram showing a step of etching a sharpened cross section of an optical fiber.
FIG. 8 is a diagram showing a step of depositing an upper electrode layer 5;
FIG. 9 is a diagram showing a step of etching all the layers deposited on the side surface of the optical fiber.
FIG. 10 is a diagram illustrating a state where etching of the side surface of the optical fiber is completed.
FIG. 11 is a diagram showing a step of etching a tip portion of an optical fiber.
FIG. 12 is a diagram showing a step of etching the upper electrode layer 5 on the side surface of the optical fiber.
FIG. 13 is a diagram showing a step of etching the insulating layer 4 on the side surface of the optical fiber.
FIG. 14 is a diagram showing a recording and reproducing principle of an optically assisted magnetic recording method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Magnetic information reproduction | regeneration probe 1a Cladding 1b Core 2 Optical fiber 2a Probe sharp part 3 Lower electrode layer 4 Insulating layer 5 Upper electrode layer 6 Conductor 7 Laser beam 8 Magnetic recording medium 9 Magnetic head 14 Magnetic field detection element 15 Thin film electrode 16 Laser light source 17 Recording medium movement support means

Claims (12)

An optical fiber having a core and a clad, and having a conical sharp portion formed at one end of the core so as to protrude from an end face of the clad, and supplying a laser beam to the recording medium; ,
A film is formed on the end face of one end of the clad of the optical fiber, and a magnetic field detecting element for detecting the magnetic field of the recording medium;
A magnetic information reproducing probe comprising: a thin film electrode for the magnetic field detection element formed on a side surface of an optical fiber.   The magnetic field detecting element is composed of an insulating compound layer and at least two ferromagnetic layers sandwiching the compound layer, and the current flowing through the compound layer is changed according to the magnetization directions of the two ferromagnetic layers. The probe according to claim 1, comprising a magnetic tunnel junction element that can be formed. One of the two ferromagnetic layers is composed of a nonmagnetic metal layer portion and two ferromagnetic layer portions separated by the nonmagnetic metal layer portion and antiferromagnetically coupled,
3. The probe according to claim 2, wherein the other ferromagnetic layer is composed of one or multiple ferromagnetic layer portions.   The probe according to claim 2 or 3, wherein the ferromagnetic layer portion is made of Fe, Co, Ni, or an alloy thereof.   The probe according to any one of claims 2 to 4, wherein at least one of the two ferromagnetic layers is in contact with an antiferromagnetic layer made of an alloy containing Mn.   The probe according to any one of claims 2 to 5, wherein the insulating compound layer is composed of a compound layer of any one of Al and Si and any of B, C, N, O, P, and S. The probe according to claim 3, wherein the nonmagnetic metal layer portion is made of a layer of Cu, Ag, or Au.   The magnetic field detection element is formed of an artificial lattice magnetic film that is configured by alternately laminating magnetic layers and conductor layers, and that can change a current flowing through the conductor layer according to a magnetization direction of the magnetic layer. The probe according to 1.   The probe according to claim 8, wherein the magnetic layer is made of a layer of Fe, Co, Ni, or a compound thereof.   The probe according to claim 8 or 9, wherein the conductor layer comprises a layer of Cu, Ag, or Au. By etching one end of the optical fiber having a core and a cladding, one end of the cladding is removed, and a conical sharpened portion is formed at one end of the core so as to protrude from the end surface of the etched cladding. A first step of projecting,
A second step of covering the sharpened portion of the optical fiber after the first step, the end face and the side surface of the clad with a thin film for a lower electrode;
A third step of covering the thin film for the lower electrode, which is placed on the sharpened portion of the optical fiber and the end face of the clad , with a multilayer thin film;
A fourth step of laminating an insulator layer on the multilayer thin film and the lower electrode thin film covered on the side surface of the optical fiber;
A fifth step of removing the insulator layer covered by the multilayer thin film in a range within a concentric circle having a radius smaller than that of an optical fiber;
A sixth step of covering the exposed multilayer thin film and insulator layer with the upper electrode thin film;
A seventh step of removing the thin film for the lower electrode, the insulator layer, and the thin film for the upper electrode laminated on the side surface of the optical fiber, leaving one strip portion along the long axis of the optical fiber;
An eighth step of removing the lower electrode thin film, the multilayer thin film and the upper electrode thin film laminated on the tip of the sharpened portion of the optical fiber;
A ninth step of exposing the insulator layer by removing a part of the thin film for the upper electrode of the band-shaped portion;
The Rukoto portion of the exposed said insulator layer is removed to expose the said thin film for the lower electrode, and an optical fiber having a conical tip portion for supplying a laser beam to the recording medium, the optical fiber A magnetic field detection element for detecting the magnetic field of the recording medium, and a thin film electrode for the magnetic field detection element formed as a thin film for upper and lower electrodes on the side surface of the optical fiber; A tenth step of obtaining a magnetic information reproducing probe comprising:
A method for manufacturing a magnetic information reproducing probe comprising : The method for manufacturing a probe for reproducing magnetic information according to claim 11, wherein the etching process in the first step is a selective chemical etching process using a mixed aqueous solution of NH ₄ F and HF.

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