JP3638504B2 - Nano magnetic head and nano magnetic head device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nanomagnetic head using a nanotube capable of inputting and outputting a magnetic signal with a precision in the nano region with respect to a magnetic recording medium made of a magnetic tape, a magnetic card, a magnetic disk, a magnetic drum, and other magnetic materials. The present invention relates to a nano magnetic head device provided with a signal control unit for inputting and outputting signals.
[0002]
[Prior art]
In general, a magnetic head is composed of a core having a magnetic pole gap and a coil wound around the core, and the magnetic gap is arranged so as to contact the magnetic recording medium. When a signal current is passed through the coil, a magnetic flux is generated in the ring-shaped core, and a part of this magnetic flux leaks from the magnetic pole gap to the magnetic recording medium, and information is magnetically recorded on the magnetic molecules of the magnetic recording medium by this leakage magnetic flux. The
[0003]
Conversely, when the magnetically recorded magnetic recording medium is moved relative to the magnetic pole gap, a signal current is generated in the coil by electromagnetic induction, and this signal current can be amplified to reproduce magnetic information. As described above, the magnetic head is a device for magnetically recording information on the magnetic recording medium and reproducing magnetic information from the magnetic recording medium.
[0004]
[Problems to be solved by the invention]
The minimum unit size of magnetic information recorded on the magnetic recording medium directly depends on the size of the magnetic pole gap formed in the core. Therefore, in order to increase the magnetic recording density, it is necessary to design the core and the magnetic pole gap portion of the core to be smaller, but as long as the formation of the core and the magnetic pole gap portion depends on machining or other physical processing, There is a size limit in miniaturization of these members. Therefore, in order to increase the magnetic recording density, not only the development of magnetic substances but also the development of core materials is urgent.
[0005]
Accordingly, an object of the present invention is to provide a nano magnetic head capable of minimizing the size of the minimum unit of magnetic information to a nano size at a stretch and achieving a significant improvement in magnetic recording density, and a nano magnetic head device using the same. It is to be.
[0006]
[Means for Solving the Problems]
In the first aspect of the invention, the base end of the nanotube is fixed to the holder so that the tip of the nanotube protrudes from the holder, the nanocoil is wound around the outer periphery of the nanotube, and a signal is input to both ends of the nanocoil. The nanomagnetic head is characterized by being output.
[0007]
In the invention of claim 2, the base end portion of the nanotube is fixed to the holder so that the tip end portion of the nanotube protrudes from the holder, the microcoil is wound around the outer periphery of the holder, and signals are input / output to both ends of the microcoil. The nanomagnetic head is characterized in that it is made to be.
[0008]
A third aspect of the present invention is the nanomagnetic head according to the first or second aspect, wherein the holder is a pyramid portion of an AFM cantilever.
[0009]
In the invention of claim 4, the base end of the nanotube is fixed to the holder so that the tip of the nanotube protrudes from the holder, and the microcoil is wound around the outer periphery of the main body that supports the holder. The nanomagnetic head is characterized in that signals are input and output at both ends.
[0010]
The invention according to claim 5 is the nanomagnetic head according to claim 4, wherein the holder is a pyramid portion of an AFM cantilever, and the main body portion is a cantilever portion of an AFM cantilever.
[0011]
A sixth aspect of the present invention is the nanomagnetic head according to the first, second, third, fourth or fifth aspect, wherein ferromagnetic metal atoms are arranged in the hollow portion of the nanotube.
[0012]
The invention according to claim 7 is composed of the nanomagnetic head according to claim 1, 2, 3, 4, 5 or 6, and a signal control unit for inputting / outputting a signal to / from the nanomagnetic head, and the nano region of the magnetic recording medium It is a nano magnetic head device that can magnetically write to and read magnetic records in the nano region.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
As a result of intensive research to develop a magnetic head capable of minimizing the size of the minimum unit of magnetic recording to the nano region, the present inventors have used nanotubes including carbon nanotubes as the core, The inventors have come up with a nano magnetic head capable of magnetically inputting / outputting from / to the magnetic recording medium by the tips of the nanotubes by utilizing micro coils and inserting the nanotubes into the hollow portions of these coils.
[0014]
That is, if electric signals are input from both ends of the nanocoil or microcoil, the magnetic flux formed by these coils is leaked from the tip of the nanotube, and magnetic recording is performed on the magnetic recording medium by this leakage magnetic flux, the minimum unit of magnetic recording The size can be minimized to the cross-sectional diameter of the nanotube.
[0015]
The reason why nanotubes are the most powerful cores is their minimal cross-sectional diameter. As the nanotube used in the present invention, there is a carbon nanotube. The cross-sectional diameters of carbon nanotubes (sometimes referred to as CNT) are distributed from about 1 nm to several tens of nm, and the axial length ranges from nano size to micron size. Therefore, if a nanotube having this high aspect ratio is used as a probe, magnetic recording can be performed in a nano size, and ultra-high magnetic recording density can be achieved.
[0016]
Following the synthesis of carbon nanotubes, BCN-based nanotubes were synthesized. For example, a mixed powder of amorphous boron and graphite is packed in a graphite rod and evaporated in nitrogen gas. Further, the sintered BN bar is packed in a graphite bar and evaporated in helium gas. Further, arc discharge is performed in helium gas using BC ₄ N as an anode and graphite as a cathode. By these methods, BCN-based nanotubes were synthesized in which some of the C atoms in CNT were replaced with B and N atoms.
[0017]
BN nanotubes were also synthesized. This is a nanotube containing almost no C atoms. For example, CNT and B ₂ O ₃ powder are put in a crucible and heated in nitrogen gas. As a result, a BN-based nanotube in which most of the C atoms in the CNT are substituted with B atoms and N atoms is synthesized.
[0018]
Since both the BCN-based nanotube and the BN-based nanotube have the same material structure as that of the CNT, the axial length ratio with respect to the diameter, that is, the aspect ratio is extremely high. Therefore, as the nanotube of the present invention, not only carbon nanotubes but also general nanotubes such as BCN-based nanotubes and BN-based nanotubes can be used.
[0019]
In general, a hollow portion is formed inside the nanotube. In order to leak the magnetic flux formed by the coil from the tip of the nanotube, it is desirable to place ferromagnetic metal atoms such as iron, cobalt, and nickel in the hollow portion of the nanotube. If ferromagnetic metal atoms are arranged in this manner, the leakage flux is reduced by these atoms, so that the sectional diameter of the leakage flux is close to the sectional diameter of the nanotube, and the magnetic recording unit can be minimized to the nano size. Since the theoretical minimum size of the cross-sectional diameter of the nanotube is about 1 nm, it is possible to minimize the minimum size of magnetic recording to 1 nm.
[0020]
Ferromagnetic metal atoms can be implanted easily. It is observed that the metal atoms naturally enter the hollow portion by simply cutting the nanotubes closed at both ends in these metal vapors or simply opening the tips. The number of ferromagnetic metal atoms injected depends on the axial length of the nanotube. In order to leak magnetic flux from the tip of the nanotube, it is desirable to fill at least the ferromagnetic metal atom in the tip.
[0021]
Even when ferromagnetic metal atoms are not arranged in the hollow portion of the nanotube, since the coil diameter is small, a nanomagnetic head can be configured. However, since the magnetic flux spreads somewhat, it is necessary to perform magnetic input / output with the tip of the coil as close to the magnetic recording medium as possible.
[0022]
The coils used in the nanomagnetic head according to the present invention include a microcoil and a nanocoil. A microcoil was first discovered and its manufacturing method was established, then a nanocoil was discovered, and its mass production method was established by the present inventors. Next, the mass production method will be described.
[0023]
An efficient method for producing carbon microcoils was discovered in 1990 by Motoshima et al. (S. Motojima, M. Kawaguchi, K. Nozaki and H. Iwanaga, Appl. Phys. Lett., 56 (1990) 321). Subsequent research has established reproducible production methods. In this method, a graphite substrate coated with a Ni powder catalyst is disposed inside a horizontal external reaction tube made of transparent quartz, and a raw material gas is introduced vertically from the upper raw material gas inlet into the substrate surface. This source gas is a mixed gas of acetylene, hydrogen, nitrogen and thiophene. The exhaust gas is discharged from the lower part.
[0024]
In particular, impurities such as sulfur and phosphorus are indispensable, and carbon microcoils do not grow if the amount of impurities is too much or too little. For example, when 0.24% of thiophene containing sulfur is added to the total gas flow rate, the coil yield is maximized, and the value is about 50%. The reaction temperature is about 750 to 800 ° C.
[0025]
The diameter of the fiber constituting the carbon microcoil is 0.01 to 1 μm, the outer diameter (outer diameter) of the coil is 1 to 10 μm, the coil pitch is 0.01 to 1 μm, and the coil length is 0.1 to 25 mm. is there. This carbon microcoil has a completely amorphous structure, has excellent physical properties such as radio wave absorption characteristics, and is expected, for example, as a radio wave absorber.
[0026]
In 1991, a carbon nanotube was discovered, and inspired by this discovery, research on a carbon coil having a nano-size outer diameter, that is, a carbon nanocoil was started. This is because there is a possibility that new physical properties may be discovered when it becomes nano-sized, and it is expected as a new material for engineering and electronics in the nano region. However, its development has not been easy.
[0027]
In 1994, Amelinks et al. (Amelinckx, XB. Zhang, D. Bernaerts, X. F. Zhang, V. Ivanov and JB. Nagy, SCIENCE, 265 (1994) 635) Successful. It was also elucidated that carbon nanocoils have a graphite structure, whereas carbon microcoils are amorphous. Various carbon nanocoils were prepared, and the minimum outer coil diameter was as small as about 12 nm. However, the coil yield is small, and it cannot be used for industrial production, and a more efficient manufacturing method has been demanded.
[0028]
Their production method is to form a metal catalyst such as Co, Fe or Ni into a fine powder, heat the vicinity of the catalyst to 600 to 700 ° C., and contact an organic gas such as acetylene or benzene. In order to decompose these organic molecules. The generated substance was a carbon nanotube having a graphite structure, and the shape thereof was linear, curved, planar spiral, coiled, or the like. That is, carbon nanocoils were only generated by chance and the coil yield was small.
[0029]
In 1999, Lee et al. (W. Li, S. Xie, W. Liu, R. Zhao, Y. Zhang, W. Zhou and G. Wang, J. Material Sci., 34 (1999) 2745) were newly introduced. We succeeded in producing carbon nanocoils. In their production method, a catalyst having iron particles coated on the outer periphery of a graphite sheet is placed in the center, and the vicinity of the catalyst is heated to 700 ° C. with a nichrome wire. A mixed gas of 10% acetylene and 90% nitrogen was circulated so as to contact the catalyst, and the flow rate was set to 1000 cc / min. There are various outer diameters of the produced carbon nanocoils, but the smaller ones were 20 nm and 22 nm. However, this production method also has a small coil production rate, and is extremely insufficient as an industrial mass production method.
[0030]
Under such circumstances, an industrial mass production method for carbon nanocoils has been established by the present inventors, and a patent application has already been filed as Japanese Patent Application No. 11-377363. In this method, an indium / tin / iron-based catalyst is placed inside the reactor, and the hydrocarbon in the vicinity of the catalyst is heated above the temperature at which the hydrocarbon used as a raw material is decomposed by catalytic action, so that the hydrocarbon comes into contact with the catalyst. In this method, carbon nanocoils are grown on the surface of a catalyst while circulating a gas and decomposing hydrocarbons in the vicinity of the catalyst. In this method, an infinite number of carbon nanocoils grow densely on the surface of the indium / tin / iron-based catalyst, and the production rate is estimated to be about 95% when calculated from the amount of hydrocarbon gas.
[0031]
The microcoils and nanocoils that can be used in the present invention are not limited to carbon microcoils and carbon nanocoils. A BN coil or BCN coil in which these C atoms are replaced with B atoms or N atoms may be used. Since an electrical signal is input to and output from the coil, the surface of the coil may be coated with a metal or metal atoms may be doped in the coil in order to ensure the electrical conductivity of the coil.
[0032]
In the present invention, the holder for fixing the nanotube is, for example, a projection for measuring an AFM cantilever, and this projection is usually called a pyramid. The shape of the pyramid portion includes a conical shape, a triangular pyramid shape, a quadrangular pyramid shape, and the like, and is a collective term for all shapes used in the AFM cantilever. The main body for fixing the holder is, for example, a cantilever portion of an APM cantilever. Of course, in addition to the AFM cantilever, other scanning probe microscope holders and other members such as STM can be used. In addition, a main body or a holder dedicated to the nano magnetic head may be created, and the nanotubes may be fixed to the holder.
[0033]
【Example】
Embodiments of a nanomagnetic head and a nanomagnetic head device according to the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a perspective view of a first embodiment of a nanomagnetic head according to the present invention. In this embodiment, a commercially available AFM cantilever is actively used. Therefore, the nanomagnetic head 2 is roughly composed of the AFM cantilever 3, the nanotube 10, and the nanocoil 12.
[0034]
The AFM cantilever 3 includes a long cantilever portion 4 and a pyramid portion 8 projecting from the tip thereof. Electrode films 6 and 6 are formed on both side edges of the cantilever portion 4. As described above, an example of the main body of the present invention is the cantilever part 4 and an example of the holder is the pyramid part 8. The base end portion 10 a of the nanotube 10 is fixed to the surface of the pyramid portion 8, and the tip end portion 10 b of the nanotube 10 protrudes from the pyramid portion 8.
[0035]
As a method of fixing the base end portion 10a of the nanotube 10 to the surface of the pyramid portion 8, for example, the surface of the base end portion 10a is covered with a carbon coating film, or the base end portion 10a is thermally fused to the pyramid portion 8. There is a way to. Electron beam irradiation or current heating can be considered as a method for heat fusion.
[0036]
The nanocoil 12 is disposed so as to wind the tip portion 10 b of the nanotube 10. Both ends of the nanocoil 12 are fused with one end of lead wires 14 and 14 using nanotubes by an electron beam to form contact points 14a and 14a. The other ends of the nanotube lead wires 14 and 14 are combined with the electrode films 6 and 6 to form contacts 14b and 14b.
[0037]
FIG. 2 is a simplified perspective view of a nanotube having ferromagnetic metal atoms arranged therein. A large number of ferromagnetic metal atoms 16, 16... Are arranged in the hollow portion 10 c of the nanotube 10. By cutting the nanotube 10 closed at both ends in metal vapor or opening the tip, metal atoms are drawn into the hollow portion 10c from the open end face. Moreover, what has a metal atom in the hollow part 10c is obtained by producing | generating the nanotube 10 in metal vapor | steam.
[0038]
FIG. 3 is a perspective view of the tip polymorph of the carbon nanotube. (A) the tip is closed with a polyhedron, (b) the tip is open, (c) the tip is closed with a cone, and (d) the tip is closed with a beak. In particular, if the closed end is the tip 10b of the nanotube 10, the encapsulated ferromagnetic metal atoms 16 are not oxidized and have a long lifetime.
[0039]
FIG. 4 is a perspective view of the nanocoil. In this example, the nanocoil 12 is formed from one carbon fiber 18, but a composite nanocoil in which two or more carbon fibers 18 are entangled in a coil shape while being well synchronized can be used in the present invention. The carbon fiber 18 is a long carbon nanotube. The size of the nanocoil 12 is generally such that the diameter d of the fiber 18 is several nanometers to several tens of nanometers, the coil diameter D is several tens of nanometers to several hundreds of nanometers, the pitch P is several nanometers to several tens of nanometers, and the axial length L is several micrometers. ~ Several tens of mm. The name of the nano coil is derived from the fact that the coil diameter D is nano size. Needless to say, when the coil diameter D is 1 μm or more, that is, a micron size, this coil is called a microcoil.
[0040]
FIG. 5 is a view showing a usage state of the nano magnetic head device according to the present invention. The magnetic head device 23 includes the nano magnetic head 2 shown in FIG. 1, a connection line 24 connected to the electrode film 6 of the cantilever part 4, and a signal control unit 25 connected to the connection line 24. . The magnetic recording medium 20 is configured by forming a magnetic film 22 on a base 21.
[0041]
First, a case where magnetic writing (magnetic input) is performed on the magnetic film 22 will be described. The tip of the nanotube 10 is brought close to the magnetic film 22, and an electric signal is sent from the signal control unit 25. The electrical signal flows through the nanocoil 12 and generates a magnetic flux inside the nanocoil 12. This magnetic flux leaks from the tip of the nanotube 10 and is recorded as magnetic information in the magnetic film 22. When the magnetic recording medium 20 is moved in the direction of arrow a, information is continuously magnetically recorded on the magnetic film 22.
[0042]
Next, a case where magnetic reading (magnetic output) is performed from the magnetic film 22 will be described. The tip of the nanotube 10 is brought close to the magnetic film 22 and the magnetic recording medium 20 is moved in the direction of arrow a. Magnetic field lines of magnetic information recorded in the magnetic film 22 enter the nanotube 10, and an induced electromotive force is generated in the nanocoil 12 by electromagnetic induction. This induced electromotive force enters the signal control unit 25 via the connection line 24, and magnetic information is continuously reproduced.
[0043]
FIG. 6 is a perspective view of a second embodiment of the nanomagnetic head according to the present invention. In this embodiment, a microcoil 26 is used instead of the nanocoil 12. The microcoil 26 is wound around a slightly larger pyramid portion 8 (an example of a holder). What is necessary is just to select and use the microcoil as much as the pyramid part 8 enters in the inside. The other parts are the same as those in FIG. 1, and the same parts are denoted by the same reference numerals and the description thereof is omitted.
[0044]
FIG. 7 is a perspective view of a third embodiment of the nanomagnetic head according to the present invention. In this embodiment, the microcoil 26 is used instead of the nanocoil 12. However, the microcoil 26 is disposed around the cantilever portion 4 (an example of the main body portion). The nanotube lead wire 14 is not used, and both ends 26 a of the microcoil 26 are fused and fixed directly to the electrode films 6 and 6. The other parts are the same as those in FIG. 1, and the same parts are denoted by the same reference numerals and the description thereof is omitted.
[0045]
FIG. 8 is a model diagram of magnetic signal enhancement when a microcoil is used. 6 and 7, the microcoil 26 is located away from the nanotube 10, but the magnetic flux formed by the microcoil 26 leaks from the tip of the nanotube 10. Therefore, if the cross-sectional area of the microcoil 26 is S, the generated magnetic flux is B, the cross-sectional area of the nanotube 10 is S ′, and the outflowing magnetic flux is B ′, then S × B = S ′ × B ′ from the continuous law. , B ′ = (S / S ′) B. That is, when the microcoil is used, the leakage magnetic flux B ′ is strengthened by the area ratio with respect to the generated magnetic flux B, so that writing to the magnetic recording medium 20 is advantageous.
[0046]
A nano magnetic head device can be configured by combining the nano magnetic head 2 shown in FIGS. 7 and 8 and the signal control unit 25, and magnetic writing and magnetic reading can be performed on the magnetic recording medium.
[0047]
The present invention is not limited to the above embodiments, and includes various modifications, design changes, and the like within the technical scope without departing from the technical idea of the present invention.
[0048]
【The invention's effect】
According to the first aspect of the present invention, since the nanomagnetic head is formed by winding the nanocoil around the nanotube, writing / reading to / from the magnetic recording medium is possible using the nanosize, which is the cross-sectional diameter of the nanotube, as the minimum unit of magnetic information. Thus, it is possible to achieve ultra-high density magnetic recording.
[0049]
According to the second aspect of the invention, since the microcoil is wound around the outer periphery of the holder and writing / reading can be performed with the nanotube, not only can the magnetic recording be realized with an extremely high density, but also the microcoil and the nanotube are disconnected during the writing. Magnetic signals can be amplified by the area ratio.
[0050]
According to the invention of claim 3, the pyramid portion of the cantilever for AFM can be used as a holder for fixing the nanotube, and a highly practical nano magnetic head can be realized at low cost.
[0051]
According to the invention of claim 4, since the microcoil is wound around the outer periphery of the main body and writing / reading can be performed with the nanotube, not only can the magnetic recording be realized with an extremely high density, but also the microcoil and the nanotube can be Magnetic signals can be amplified by the cross-sectional area ratio.
[0052]
According to the invention of claim 5, since the microcoil is wound around the cantilever part, a highly practical nano magnetic head using a commercially available AFM cantilever can be realized at a low price, and the magnetic signal for writing is interrupted. Only the area ratio can be amplified.
[0053]
According to the invention of claim 6, since the ferromagnetic metal atoms are arranged in the hollow portion of the nanotube, not only the magnetic flux density can be enhanced, but also the magnetic flux density inputted to and outputted from the nanotube can be narrowed down and high performance can be achieved. Nano magnetic head can be realized.
[0054]
According to the invention of claim 7, since the nano magnetic head can be operated by the signal control unit, a nano magnetic head device capable of magnetically writing to the nano area of the magnetic recording medium and reading the magnetic record of the nano area can be provided. . .
[Brief description of the drawings]
FIG. 1 is a perspective view of a first embodiment of a nanomagnetic head according to the present invention.
FIG. 2 is a simplified perspective view of a nanotube having ferromagnetic metal atoms arranged therein.
FIG. 3 is a perspective view of a carbon nanotube tip polymorph.
FIG. 4 is a perspective view of a nanocoil.
FIG. 5 is a diagram showing a usage state of the nano magnetic head device according to the present invention.
FIG. 6 is a perspective view of a second embodiment of the nanomagnetic head according to the present invention.
FIG. 7 is a perspective view of a third embodiment of the nanomagnetic head according to the present invention.
FIG. 8 is a model diagram of magnetic signal enhancement when a microcoil is used.
[Explanation of symbols]
2 ... Nano magnetic head 3 ... AFM cantilever 4 ... Cantilever part 6 ... Electrode film 8 ... Pyramid part 10 ... Nanotube 10a ... Base end part 10b ... Tip part 10c · Hollow portion 12 · · · Nanocoil 14 · · · Nanotube lead wire 14a · · Contact 14b · · Contact 16 · · · Ferromagnetic metal atom 18 · · · Carbon fiber 20 · · · Magnetic recording medium 21 · · · Base 22 ... Magnetic film 23 ... Nano magnetic head device 24 ... Connection line 25 ... Signal control unit 26 ... Microcoil 26a ... Contact d ... Fiber diameter D ... Coil diameter L ... ..Axis length P ... Pitch

Claims (9)

The distal end portion of the nanotube is fixed to the holder base end portion of the nanotube as to protrude from the holder, the nanocoil the outer periphery of the distal end portion of the nanotube wound arrangement, connecting one end of the nanotube leads to at least one end of the nanocoil Then, a nanomagnetic head characterized in that signals are inputted to and outputted from the nanocoil through the nanotube lead wires . The distal end portion of the nanotube is fixed to the holder base end portion of the nanotube as to protrude from the holder, the microcoil outer periphery of the holder wound arrangement, to connect one end of the at least one end to the nanotube leads of the microcoil A nanomagnetic head, wherein a signal is inputted to and outputted from the microcoil through the nanotube lead wire . The base end of the nanotube is arranged on the holder so that the tip of the nanotube protrudes from the holder , the base end is fixed to the holder surface by a carbon coating film or fusion, and the nanocoil is placed on the outer periphery of the tip of the nanotube. the wound arrangement, nano magnetic head, characterized in that for input and output signals to both ends of the nanocoil. The base end of the nanotube is arranged on the holder so that the tip of the nanotube protrudes from the holder , the base end is fixed to the holder surface by a carbon coating film or fusion, and a microcoil is wound around the outer periphery of the holder. and instrumentation arrangement, nano magnetic head, characterized in that for input and output signals to both ends of the microcoil. The distal end portion of the nanotube is fixed to the holder base end portion of the nanotube as to protrude from the holder, the micro-coil is wound around arranged on the outer circumference of the main body portion for supporting the holder, input and output signals to both ends of the microcoil Nano magnetic head characterized in that   The nanomagnetic head according to claim 1, wherein the holder is a pyramid portion of an AFM cantilever. 6. The nanomagnetic head according to claim 5, wherein the holder is a pyramid portion of an AFM cantilever, and the main body portion is a cantilever portion of an AFM cantilever.   The nanomagnetic head according to claim 1, wherein ferromagnetic metal atoms are arranged in a hollow portion of the nanotube.   The nanomagnetic head according to any one of claims 1 to 8, and a signal control unit that inputs and outputs a signal to the nanomagnetic head, and magnetically writes to the nanoregion of the magnetic recording medium or magnetic recording of the nanoregion Nano magnetic head device that can read.

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