JP2012022760A - Information recording head, information recording device, information recording method, and optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording head, an information recording device, and an information recording method, realizing high-speed recording and high-density recording simultaneously in information recording by means of direct magnetization reversal by circular polarization.SOLUTION: A plasmon antenna 22 having a rotationally symmetrical opening 22A having a shape that is roughly rotationally symmetrical around an axis in the direction of progress of recording light radiated at a nanometer size that is larger than bit carriers 15 on bit patterned media 10 is irradiated with femtosecond pulse laser light as the above-described recording light, and is excited by the femtosecond pulse laser light radiated as the recording light at the plasmon antenna 22, and by means of interaction of the bit carrier 15 on the bit patterned media 10 positioned facing the rotationally symmetrical opening 22A of the plasmon antenna 22 and the rotationally symmetrical opening 22A of the plasmon antenna 22, circularly polarized light is generated within the bit carrier 15 and information is recorded by means of direct magnetization reversal.

Description

  The present invention has an information recording head for recording information on a recording medium having a recording layer in which recording medium particles are dispersed, an information recording apparatus, an information recording method, and a function of changing a magnetic effect by laser light irradiation. It relates to the optical device method.

  In the information society in recent years, digitalization has accelerated and the demand for large capacity recording devices has been increasing. What is currently put into practical use as a magnetic recording apparatus is a magnetic recording medium having a ferromagnetic polycrystalline thin film.

  This is also called a granular type, in which a ferromagnetic polycrystalline thin film composed of a plurality of magnetic particles having high uniaxial magnetic anisotropy is provided on a medium, and magnetic particles are contained in one bit of recorded information. It is included in multiple numbers. As the recording density increases, the number of magnetic particles contained in one bit decreases, so that the magnetic flux decreases and noise increases. Until now, we have been increasing the density by reducing the size of the magnetic particles, but if the particle size is made smaller than this, the energy to hold magnetic information will be insufficient, and the thermal energy will be about room temperature. The information will be lost. Therefore, the use of a recording material having high magnetic stability has been studied as one method for increasing the density. However, when the stability of the magnetic particles is high, there is a problem that recording with a conventional magnetic head becomes impossible. For this reason, there has also been proposed an optically assisted magnetic recording apparatus that performs recording by temporarily reducing the coercive force of magnetic particles with heat (light) before recording with a magnetic head. Furthermore, in order to achieve higher density, bit patterned media has been proposed in which a magnetic recording layer is separated also in the track longitudinal direction and one magnetic particle is recorded as one bit. This is a structure in which a magnetic layer is physically separated for each magnetic particle, and a magnetic material is evenly arranged as a bit carrier in the track longitudinal direction (see, for example, Patent Document 1).

  The inventors of the present application, as a bit-patterned medium that records one magnetic particle as one bit, laminates an underlayer on which a minute concave portion is uniformly exposed on a substrate. An amorphous magnetic film is laminated on the surface of the underlayer in which the concave portion is exposed. The underlayer is made of tetraethoxysilane as a raw material, and is spherical in self-alignment evenly in a face-centered cubic structure. By removing the micelles, it is a layer made of silicon oxide in which spherical holes of the same size are uniformly formed in a face-centered cubic structure, and evenly on the surface on which the amorphous magnetic film is laminated A magnetic recording medium that has been surface-treated so that minute concave portions are exposed has been proposed (for example, see Patent Document 2).

  Magnetic disk memory is an important file memory system that supports today's computer society, but the physical limit of the response speed of magnetic materials is approaching, and large-capacity data will be recorded at an appropriate speed in the near future. Becomes impossible.

  As a new method for overcoming this problem, the inventors of the present application have proposed a recording method using circularly polarized light in which the magnetization state is controlled by circularly polarized light (see, for example, Non-Patent Document 1 and Patent Document 3). ).

  That is, a magneto-optic comprising a magnetizable medium and an irradiation system adapted to impart angular momentum to the magnetic spin system of the magnetizable medium so as to selectively orient the magnetization of the medium The switching element allows information “bits” to be recorded as regions of opposite magnetization or spin.

  The spin states in the magnetic material can be manipulated using appropriate angular momentum irradiation, in particular using circularly or elliptically polarized light. An effective magnetic field is generated to orient the magnetization of the magnetic domains and can be used to locally heat the material at the same time.

  Circularly polarized laser pulses act on spins via spin orbit coupling as an effective magnetic field, and this effect is known as the inverse Faraday effect. The magnitude of this magnetic field is proportional to the magneto-optic constant that does not vary with temperature in the first order approximation. Therefore, phenomenologically, the overall effect is the heating of the magnetic system plus the application of an effective magnetic field due to the inverse Faraday effect. Switching is very efficient due to the magnetic susceptibility diffusing near the Curie temperature.

Specifically, the magnetization reversal can be performed only by single pulse irradiation with a pulse length of 40 fs (femtosecond: 10 ⁻¹⁵ seconds) to the GdFeCo thin film using circularly polarized light using a femtosecond pulse laser as a light source. The light-spin action is equivalent to the application of a magnetic field in the direction of light travel, and can be controlled by selecting a circularly polarized helicity (clockwise or counterclockwise). I can explain.

JP 2009-163816 A WO2005 / 081233 Special table 2009-538490 gazette

“All-Optical Magnetic Recording with Circularly Polarized Light”, C. D Stanciu et. Al .: Physical Review Letters, Vol. 99, 047601 (2007). “Circularly and elliptically polarized near-field radiation from nanoscale subwavelength apertures”, Erdem Ogut et. Al .: Applied Physics Letters, Vol. 96 141104 (2010). "Circular polarization analysis in the vicinity of nano-sized cross-shaped aperture antenna", Takeshi Ota, Yoshito Serizawa, Koji Nakagawa, 33rd Annual Meeting of the Magnetics Society of Japan (2009)

  Conventional magneto-optical recording uses the fact that the temperature rises due to light, so that the writing speed is inherently slow, and when the writing area becomes small, the magnetization becomes unstable and information is lost. .

  In the recording method using circularly polarized light that has been proposed by the inventors of the present application to control the magnetization state with circularly polarized light, high-speed magnetization reversal can be achieved by circularly polarized light without an external magnetic field. With this technique, it is difficult to increase the recording density even though high-speed recording is possible. That is, in high-density recording, although it is necessary to locally generate circularly polarized light, light can be focused only to the order of the wavelength due to the physical limitation of the diffraction limit of light.

  By the way, it has been reported that plasmon resonance occurs in circularly polarized light (see, for example, Non-Patent Document 2), and the use of near-field light can be considered to produce local circularly polarized light.

  The inventors of the present application conducted a circular polarization analysis in the vicinity of the nanometer-size cross-shaped aperture antenna and announced that a mode close to circular polarization near the nanometer-size cross-shaped aperture antenna can be formed with the recording medium disposed. (For example, refer nonpatent literature 3).

  Accordingly, an object of the present invention is to provide an information recording head, an information recording apparatus, and an information recording apparatus that simultaneously realize high speed and high density in recording information by direct magnetization reversal by circularly polarized light in view of the conventional situation as described above. It is to provide a method.

  Another object of the present invention is to provide an optical device method having a function of changing a magnetic effect by irradiation with laser light.

  In the present invention, in order to solve the above-mentioned problem, the interaction between the recording medium particles and the nanometer-sized rotationally symmetric opening having a substantially rotational symmetry with the traveling direction of the irradiated recording light as an axis. Is used to generate circularly polarized light locally in the recording medium particles and record information by direct magnetization reversal.

  That is, the present invention is an information recording head for recording information with a laser beam on a recording medium having a recording layer in which recording medium particles are dispersed, and the upper recording medium dispersed in the recording layer of the recording medium A plasmon antenna having a shape with substantially rotational symmetry about the traveling direction of the recording light irradiated with a size larger than the particle, and excited by the laser light applied as the recording light to the plasmon antenna, Directly magnetized by generating circularly polarized light or elliptically polarized light in the recording medium particles due to the interaction between the recording medium particles dispersed in the recording layer of the recording medium positioned facing the antenna and the plasmon antenna. Information is recorded by inversion.

  In the information recording head according to the present invention, the rotational symmetry of the plasmon antenna is preferably four-fold symmetry.

  The present invention also relates to an information recording apparatus, comprising: a recording medium having a recording layer in which recording medium particles are dispersed; and a substantially rotation about an advancing direction of recording light irradiated with a larger size than the upper recording medium particles A plasmon antenna having a symmetrical shape; and a light source for irradiating the plasmon antenna with laser light as the recording light. The plasmon antenna is excited by the laser light irradiated as the recording light, and is applied to the plasmon antenna. Due to the interaction between the recording medium particles dispersed in the recording layer of the recording medium facing each other and the plasmon antenna, circularly or elliptically polarized light is generated in the recording medium particles, and direct magnetization reversal. It is characterized by recording information.

  In the information recording apparatus according to the present invention, the rotational symmetry is preferably four-fold symmetry.

  In the information recording apparatus according to the present invention, the light source may emit a short pulse laser beam.

  In the information recording apparatus according to the present invention, the recording medium may be a bit patterned medium in which a plurality of bit carriers for recording one magnetic particle as one bit are arranged.

  Furthermore, in the information recording apparatus according to the present invention, the recording medium can be a recording medium having a granular structure in which nanoscale fine metal particles are dispersed in an insulating matrix.

  The present invention also relates to an information recording method for recording information on a recording medium having a recording layer in which recording medium particles are dispersed with a laser beam, the traveling direction of the recording light irradiated with a size larger than the recording medium particles. A laser beam as the recording light is irradiated to a plasmon antenna having a substantially rotational symmetry with the axis as the axis, excited by the laser light irradiated as the recording light to the plasmon antenna, and opposed to the plasmon antenna. Information is recorded by direct magnetization reversal by generating circularly or elliptically polarized light in the recording medium particles by the interaction of the recording medium particles dispersed in the recording layer of the recording medium positioned and the plasmon antenna. It is characterized by doing.

  The information recording method according to the present invention can irradiate the plasmon antenna having four-fold symmetry with a short pulse laser beam as the recording light.

  Furthermore, the present invention is an optical device having a function of changing a magnetic effect by laser light irradiation, wherein the magnetic particle part whose magnetization direction is changed by the laser light irradiation is arranged in contact with the magnetic particle part. At least one magnetic body portion and a plasmon antenna having a substantially rotational symmetry with the traveling direction of laser light irradiated in a larger size than the magnetic particle portion as an axis, and irradiating the plasmon antenna Generated by circularly or elliptically polarized light in the magnetic body portion by the interaction between the plasmon antenna and the magnetic body portion which is excited by the laser beam and is positioned opposite to the plasmon antenna. Thus, the magnetic action of the magnetic body portion arranged in contact with the magnetic particle portion is changed.

  An optical device according to the present invention includes two magnetic body portions arranged in contact with the magnetic particle portion, and circularly polarized light or elliptical light is formed in the magnetic body portion by interaction between the magnetic body portion and the plasmon antenna. It is possible to change the magnetoresistance between two magnetic body portions arranged in contact with the magnetic particle portion by generating polarized light and directly reversing the magnetization.

  According to the present invention, a plasmon antenna having a rotationally symmetric aperture having a substantially rotational symmetry with the traveling direction of recording light irradiated at a nanometer size larger than the recording medium particles as an axis is irradiated as the recording light. Recording medium particles excited by the femtosecond pulsed laser light and dispersed in the recording layer of the recording medium located opposite the rotational characteristic aperture of the plasmon antenna, and a rotationally symmetric aperture of the plasmon antenna By generating circularly polarized light in the above recording medium particles and directly recording information by magnetization reversal, the high speed and high density can be realized at the same time. Although only size recording could be performed, recording at a size of several tens of nanometers can be made possible.

  That is, according to the present invention, in recording information by direct magnetization reversal by circularly polarized light, due to the interaction between the recording medium particles dispersed in the recording layer of the recording medium and the rotationally symmetric aperture of the plasmon antenna, By generating circularly polarized light in the recording medium particles and recording information by direct magnetization reversal, it is possible to provide an information recording head, an information recording apparatus, and an information recording method that simultaneously realize high speed and high density. .

  In the present invention, the magnetic body portion excited by the laser light applied to the plasmon antenna and positioned opposite to the plasmon antenna and the plasmon antenna interacts with the circularly polarized light in the magnetic body portion. By generating elliptically polarized light and directly reversing the magnetization, the magnetic action of the magnetic body portion arranged in contact with the magnetic particle portion can be changed.

It is a perspective view which shows schematic structure of the information recording device to which this invention is applied. It is a block diagram which shows typically the principal part structure of a structure of the said information recording device. It is a schematic diagram which shows the simulation model of the plasmon head with which the information recording head in the said information recording device is equipped. It is a figure which shows typically the structural example of the solid antenna of the solid shape which has rotational symmetry. It is a figure which shows typically the structural example of a 4-fold symmetry antenna. It is a figure which shows typically the structural example of a two-fold symmetry antenna. It is a figure which shows the time distribution of the electromagnetic field of a 4-fold symmetrical aperture type antenna. It is a diagram showing the electric field and the phase difference of the magnetic field θ in Poynting vector S _Z and the X-Y plane of the magnetic media direction (+ Z direction) at the opening center of the observation point of the 4-fold symmetry aperture antenna. It is a diagram showing the spatial distribution of the Z-direction component S _Z of the Poynting vector in the cross-gated antenna and circular aperture antenna. It is a schematic diagram showing a simulation model of a cross aperture antenna in which a cross-shaped opening (Cross aperture) is opposed to a Co continuous recording medium. It is a figure which shows the dependence with respect to the length L of the long side of the opening part of angle (theta) which the electric field E and the magnetic field H in the simulation model XY plane of the cross opening antenna shown in the said FIG. 10 make. When there is no antenna, it is a figure which shows the result of having evaluated each circular polarization degree C on Co continuous recording medium in the simulation model of a cross aperture type antenna and a circular aperture type antenna. It is a figure which shows each circular polarization degree C on the A-A 'line, the A-B line, and the A-A' line in FIG. When there is no antenna, it is a figure which shows the result of having evaluated each electric field strength I on Co continuous recording medium in the simulation model of a cross aperture type antenna and a circular aperture type antenna. It is a figure which shows each electric field strength I on the A-A 'line, the A-B line, and the A-A' line in FIG. When there is no antenna, it is a figure which shows the result of having evaluated each performance index F on the Co continuous recording medium in the simulation model of a cross aperture type antenna and a circular aperture type antenna. It is a figure which shows each figure of merit F on the A-A 'line, the A-B line, and the A-A' line in FIG. In the plasmon head shown in FIG. 3, it is a figure which shows the simulation model which simulates the pointing vector S, the electric field E, the magnetic field H, and its phase difference (theta) in the observation position on a bit carrier. It is a figure which shows the circular polarization degree S, the electric field strength I, and the figure of merit F in the XZ plane of the simulation model of a cross opening type antenna. The cross-gated antenna of the simulation model of X-Z plane circular polarization in degree S, and the direction cosine S _{Z /} recording medium direction (+ Z direction) | is a diagram showing a | S. It is a diagram illustrating a | the cross-gated phase difference distribution of the recording medium direction at the center of the simulation model of the antenna (+ Z direction) and the direction cosine S _{Z /} | S. Continuous recording medium phase difference distribution and the direction cosines of the recording medium direction (+ Z direction) at the center of the simulation model of the simulation model and without antenna cross-gated antenna is opposed to S _{Z /} | S | is a diagram showing a. Continuous recording medium phase difference distribution and the direction cosines of the recording medium direction (+ Z direction) at the center of the simulation model of the simulation model and without antenna cross-gated antenna is opposed to S _{Z /} | S | is a diagram showing a. It is a schematic diagram which shows the other simulation model of the plasmon head with which the information recording head in the said information recording device is equipped. The plasmon degree of circular polarization in the X-Z plane of another simulation model of head S ', the direction cosine S _{Z /} recording medium direction (+ Z direction) | S |, and the field intensity I' is a diagram showing a. In another simulation model of the plasmon head, the degree of circular polarization S ′ in the XZ plane when the incident circularly polarized light is reversed, the direction cosine S _Z / | S | in the recording medium direction (+ Z direction), and It is a figure which shows electric field strength I '. It is a figure which shows typically the structural example of the magneto-resistive effect device to which this invention is applied.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  The present invention is applied to an information recording apparatus 100 that records information on a bit patterned medium 10 in which a plurality of bit carriers 15 made of a magnetic material are arranged on a medium substrate as shown in FIGS. 1 and 2, for example.

  The information recording apparatus 100 includes a bit patterned medium 10, an information recording head 20, a detection unit 30, and a control unit 40, and directly detects the arrangement position of the bit carrier 15 of the bit patterned medium 10 by the detection unit 30. Then, the recording operation is controlled by the control unit 40 using the detection signal as a recording clock signal, and information is recorded on the bit carrier 15 of the bit patterned medium 10 by the information recording head 20 bit by bit. is there.

In the bit patterned medium 10 used as a recording medium, a plurality of bit carriers (recording carriers) 15 made of a magnetic material are arranged on a substrate. The bit carrier 15 is formed so that one bit corresponds to one bit carrier, for example, by a semiconductor manufacturing process or the like. For example, as shown in a partially enlarged view of FIG. Thus, it is separated into a magnetic region serving as a bit carrier and a nonmagnetic region serving as the other region. It should be noted that the present invention is not limited to the bit patterned medium formed with physical unevenness, and any structure may be used as long as the medium is configured to be a 1-bit carrier. For example, a medium that is magnetically separated by changing the composition or the film structure may be used. For example, a high-density magnetic fine particle film is fabricated using a SiO ₂ film having nanoscale vacancies inside a face-centered cubic structure using the self-organization phenomenon of a polymer as an underlayer. Ultra-high density recording medium in which nanometer-sized magnetic fine particles with high packing density are formed on a template substrate on which nanometer-size irregularities are exposed by periodically arranging the surface of a porous SiO ₂ film by Ar ion etching Can be used.

  The information recording head 20 is excited by a light source unit 21 using a semiconductor laser that emits a recording laser beam whose emission timing is controlled by the control unit 40, and a laser beam emitted as the recording light from the light source unit 21, It comprises a plasmon antenna 22 having a nanometer-size opening 22A for generating circularly polarized light inside the bit carrier 15 on the bit patterned medium 10.

  For the light source unit 21, a semiconductor laser that emits laser light having a wavelength λ of 780 nm, for example, is used as the recording laser light. The light source unit 21 emits a femtosecond pulsed laser beam having a wavelength λ of 780 nm, for example, as a recording laser beam whose emission timing is controlled by the control unit 40.

  The detection unit 30 detects the arrangement position of the bit carrier 15 before recording on the bit carrier 15 by the information recording head 20. That is, the detection unit 30 detects the arrangement position of the bit carrier 15 to be recorded before recording. The bit carrier 15 is manufactured by a high-precision process. However, as the arrangement pitch of the bit carrier 15 becomes finer, for example, 25 nm pitch in order to increase the recording density, the influence of the displacement of the arrangement position due to the production error can be ignored. It will disappear. The detection unit 30 is provided to detect the arrangement position of the bit carrier 15 in order to compensate for this deviation, detects the arrangement position of the bit carrier 15, and based on this, the correlation signal corresponding to this arrangement position is detected. Is output.

  Various methods for detecting the arrangement position of the bit carrier 15 can be used. As an example, there is one that detects a physical phenomenon change caused by the position of the bit carrier 15. Examples of the physical phenomenon change include a light intensity change, a capacitance change, a magnetic change, an eddy current change, and a sound wave reflection time change with respect to the bit carrier 15. For example, when the bit carrier 15 is irradiated with light, the near-field light intensity changes depending on the arrangement position of the bit carrier 15, and this is detected. Further, when detecting the capacitance, the fact that the capacitance between the metal plates changes depending on the arrangement position of the bit carrier 15 is utilized. Similarly, the change in hardness can be detected by detecting the change in magnetism with a magnetic sensor, detecting the change in eddy current generated in the metal plate, or measuring the time when the reflected wave returns by irradiating ultrasonic waves. By detecting it, the arrangement position of the bit carrier 15 can be detected.

  The control unit 40 controls the recording timing of the information recording head 20 on the bit carrier 15 using the correlation signal obtained by the detection unit 30. That is, after the position of the bit carrier 15 is detected, the information recording head 20 performs recording in accordance with the arrangement position. The control unit 40 only needs to be configured to output a clock signal that determines the recording timing by the information recording head 20, and by using a correlation signal corresponding to a change in the arrangement position of the bit carrier 15 as this clock signal. The arrangement position of the bit carrier 15 can be detected and used as it is as a clock signal. Therefore, for example, even if the bit carrier 15 to be arranged at a pitch of 45 nm changes the distance between the individual bit carriers to 44 nm or 46 nm due to a manufacturing error, the arrangement position changes before recording by the information recording head 20. Can be detected by the detection unit 40, and recording can be accurately performed on the bit carrier 15 at the same timing. Note that recording may be performed by outputting a clock signal delayed by a predetermined timing depending on the relationship between the rotation speed of the recording medium and the distance between the information recording head and the detection unit.

  The information recording apparatus 100 excites the plasmon antenna 22 by irradiating the plasmon antenna 22 having the nanometer size opening 22A with femtosecond pulsed laser light having a wavelength λ of 780 nm emitted from the light source unit 21. Then, circularly polarized light is locally generated by the interaction between the plasmon antenna 22 and the bit carrier 15 on the bit patterned medium 10. As a result, the bit carrier 15 is directly magnetized by circularly polarized light without an external magnetic field, and 1-bit information is recorded.

  The light source unit 21 is provided outside the information recording head 20, and a light guide path for irradiating the plasmon antenna 22 with femtosecond pulsed laser light having a wavelength λ of 780 nm emitted from the light source unit is provided to the information recording head 20. You may make it provide.

  The plasmon antenna 22 that generates circularly polarized light locally by interaction with the bit carrier 15 on the bit patterned medium 10 has a nanometer-sized shape having rotational symmetry about the traveling direction of light. An aperture antenna having an aperture 22A is used.

  For example, as shown in FIG. 3A and FIG. 3B, a long side L = 150 nm and a short side W = square are formed on a silver (Ag) plate 22B having a square of 2000 nm in both length and width and a thickness of 35 nm. A cross aperture type antenna provided with a cross aperture 22 </ b> A in which a 20 nm rectangle is orthogonal is used as the plasmon antenna 22.

  That is, the information recording head 20 in the information recording apparatus 100 records information on a recording medium having a recording layer in which recording medium particles are dispersed by femtosecond pulsed laser light. The rotational symmetry of the shape having rotational symmetry about the traveling direction of the recording light irradiated with the nanometer size larger than the recording medium particles, that is, the bit carrier 15 on the bit patterned medium 10 dispersed in the layer The recording is provided with a plasmon antenna 22 having an opening 22A, and is excited by femtosecond pulsed laser light applied to the plasmon antenna 22 as the recording light, and is positioned facing the rotationally symmetric opening 22A of the plasmon antenna 22. Recording medium particles dispersed in the recording layer of the medium, and the plasmon antenna 22 By interaction with rotational symmetry openings 22A, information is recorded by direct magnetization reversal by generating a circularly polarized light on the recording medium in the particles.

  Here, the electromagnetic field in the vicinity of the aperture antenna using “Poynting” manufactured by Fujitsu, which is a commercially available general-purpose three-dimensional electromagnetic analysis software, as simulation software for the FDTD method (Finite-difference time-domain method; FDTD method). As a result of simulation, the following results were obtained.

In the simulation model, incident light is incident in the + Z-axis direction, is circularly polarized light having a wavelength λ = 780 nm, the intensity distribution is a Gaussian distribution having a central peak electric field of 1 V / m, and a Gaussian radius is 780 nm (Intensity = 1 / e ² ). The minimum cell size was 1 × 1 × 1 nm ³ .

  Here, as the rotationally symmetric antenna, an aperture antenna or a linear antenna having a rotational symmetry, or a three-dimensional solid having rotational symmetry as shown in, for example, (A) to (D) of FIG. There are antennas 110A, 110B, 110C, and 110D.

As shown in FIGS. 5A to 5D, the four-fold symmetry antenna has two sets of aperture antennas, linear antennas, or three-dimensional antennas formed in a shape having rotational symmetry. It has a structure arranged symmetrically.
The four-fold symmetry antenna 221A shown in FIG. 5A is a four-fold symmetry aperture antenna in which an opening having four-fold symmetry is provided in a metal plate.

  A four-fold symmetry antenna 221B shown in FIG. 5B is a four-fold symmetry linear antenna in which linear antennas are arranged so as to have four-fold symmetry.

  A four-fold symmetric antenna 221C shown in FIG. 5C is a four-fold symmetric three-dimensional antenna in which spherical three-dimensional antennas having a four-fold symmetry are arranged so as to have four-fold symmetry.

  A four-fold symmetry antenna 221D shown in FIG. 5D is a four-fold symmetry three-dimensional antenna in which spherical three-dimensional antennas having a rotation symmetry are arranged so as to have four-fold symmetry.

  In addition, the two-fold symmetric antenna has a structure in which the size and shape of two opposing sets of rotationally symmetric antennas are changed as shown in FIGS. 6A to 6D as structural examples.

  That is, the two-fold symmetric antenna 222A shown in FIG. 6A is a two-fold symmetric aperture antenna having two sets of rotationally symmetric apertures of different sizes provided so as to have a two-fold symmetry in a metal plate. .

  A two-fold symmetrical antenna 222B shown in FIG. 6B is a two-fold symmetrical linear antenna in which two sets of linear antennas having different sizes are arranged so as to have two-fold symmetry.

  A two-fold symmetrical antenna 222C shown in FIG. 6C is a two-fold symmetrical three-dimensional antenna in which two sets of spherical three-dimensional antennas having different sizes are arranged so as to have two-fold symmetry. .

  A two-fold symmetrical antenna 222D shown in FIG. 6D is a two-fold symmetrical three-dimensional antenna in which two sets of spherical three-dimensional antennas having different sizes are arranged so as to have two-fold symmetry. .

  For example, circularly polarized light can be generated with a phase difference due to a difference in resonance conditions of the major axis and the minor axis by, for example, entering linearly polarized light having an electric field vector in a direction inclined about 45 ° with respect to the symmetry axis. That is, the plasmon antenna 22 may be an antenna having two-fold symmetry in principle.

FIG. 7 shows the time distribution of the electromagnetic field of a cross-opening antenna provided with a cross-shaped aperture (Cross aperture) in which rectangles having a long side L = 150 nm and a short side W = 20 nm are orthogonal to each other. of (a), as shown (B), the electric field component equal and the X-direction component _{E X} and Y-direction component _{E Y,} the magnetic field component in the X direction component _{H X} and Y-direction component _{H Y} size Are equal, and the phase difference between the electric field component and the magnetic field component is shifted by λ / 4.

Then, the pointing vector S _Z in the magnetic medium direction (+ Z direction) and the phase difference θ between the electric field and the magnetic field in the XY plane at the central observation point of the four-fold symmetric aperture antenna are shown in FIG. , (B), the four-fold symmetrical aperture antenna has a propagation direction and a phase difference θ between the electric field and the magnetic field when S _Z /|S|>0.95.
^{_{θ = tan -1 (E X /}} E Y) -tan -1 (H X / H Y)
Is suitable for use as a plasmon antenna that generates circularly polarized light.

In addition, as shown in FIG. 9, the spatial distribution of the Z-direction component S _Z of the pointing vector in the cross aperture antenna and the circular aperture antenna propagates high energy locally in the cross aperture antenna.

  Therefore, as shown in FIGS. 10A and 10B, a cross-shaped aperture (Cross aperture) 22A ′ in which rectangles having a long side length L and a short side length W are orthogonal to each other is made of silver (Ag). ) For the simulation model of the cross aperture antenna provided on the manufactured plate 22B ′, L = 100 to 400 nm, W = 20 nm, incident light is incident in the + Z-axis direction, circularly polarized light having a wavelength λ = 780 nm, and intensity distribution Is a Gaussian distribution with a central peak electric field of 1 V / m, and in a simulation model in which the Co continuous recording medium 150 is arranged with a distance FH = 5 nm between the medium and the antenna, the pointing vector S, the electric field E, and the magnetic field H at a position of 1 nm on the recording medium. The phase difference θ was evaluated and compared with the case without the recording medium.

  In the circular polarization mode analysis, in addition to the electric field E and the magnetic field H being in the rotation mode in synchronization with the incident circular polarization, the pointing vector S is stably directed to the recording medium direction (+ Z axis direction). Focused on being.

When there was no recording medium, a phenomenon in which the orientation of the pointing vector S randomly changed in the + Z-axis direction and the −Z-axis direction when the long side L of the opening was 250 nm or more appeared. Further, when the long side L of the opening is in the range of 100 nm to 200 nm, the pointing vector S always indicates the + Z axis direction, and the direction cosine (S _Z / | S |) is always 0.995 or more. At this time, the dependence of the angle θ formed by the electric field E and the magnetic field H in the XY plane on the length L of the long side of the opening is shown in FIG. Depends greatly on the change.

On the other hand, when the recording medium is arranged, the angle θ between the electric field E and the magnetic field H in the XY plane is always 90 ° to 130 ° regardless of the length L of the long side of the opening within the analyzed range. The direction cosine (S _Z / | S |) was always 0.995 or more.

  As described above, a mode close to circularly polarized light can be formed in the vicinity of the nanometer-sized cross aperture antenna with the recording medium disposed.

Here, a parameter S _I indicating the intensity of light, a parameter S _Q indicating a horizontal dominant component, a parameter S _C indicating a + 45 ° dominant component, and a parameter S _S indicating a circular dominant component are represented by the Stokes parameter S expressed by the average value of the electric field. _I , S _Q , S _C , S _S
S _I = <E _X2 > + <E _Y2 >
S _Q = <E _X2 > − <E _Y2 >
S _C = <2E _X E _Y cosr>
_{S S = <2E X E Y} sinr>
As shown in Table 1, it is possible to evaluate what kind of polarized light is, that is, clockwise circularly polarized light, linearly polarized light, linearly polarized light shifted by 45 °, or elliptically polarized light.

Here, E _X represents the X component of the electric field, E _Y represents the Y component of the electric field, r represents the phase difference between the X component E _X and the Y component E _Y of the electric field, and <> represents the time average.

In the case of no antenna, the circular polarization degree C and the electric field strength are obtained by using the following equations obtained by extending the Stokes parameters S _I , S _Q , S _C , and S _S for the simulation models of the cross aperture antenna and the circular aperture antenna. The results of evaluation of I and performance index F are shown in FIGS.

C = <2E _X E _Y sinr> / (<E _X2 > + <E _Y2 > + <E _Z2 >)
I = <E _X2 > + <E _Y2 > + <E _Z2 >
F = C × I = <2E _X E _Y sinr>
Here, E _X is the X component of the electric field, E _Y is the Y component of the electric field, E _Z is the Z component of the electric field, r is the phase difference between the X component E _X and the Y component E _Y of the electric field, and <> is the time average To express.

  (A), (B), and (C) of FIG. 12 show the circularly polarized light on the Co continuous recording medium 250 when there is no antenna, when a cross aperture antenna is provided, and when a circular aperture antenna is provided. FIG. 13 shows the degree of circular polarization C on the lines AA ′, AB and AA ′ in FIGS. 12A, 12B and 12C. Yes.

  (A), (B), and (C) of FIG. 14 show the electric field strengths on the Co continuous recording medium 250 when there is no antenna, when a cross aperture antenna is provided, and when a circular aperture antenna is provided. 15 shows each electric field intensity I on the AA ′ line, the AB line, and the AA ′ line in FIGS. 14A, 14B, and 14C.

  (A), (B), and (C) of FIG. 16 show the performance indexes on the Co continuous recording medium 250 when there is no antenna, when a cross aperture antenna is provided, and when a circular aperture antenna is provided. FIG. 17 shows each figure of merit F on the AA ′ line, AB line, and AA ′ line in FIGS. 16A, 16B, and 16C.

  However, with a cross aperture antenna or a circular aperture antenna, high energy can be propagated to a region within the aperture range, and in particular, with a cross aperture antenna, high energy can be propagated locally. However, there is a possibility that a region where the electric field intensity I is high is formed at the edge portion of the opening, and recording is performed up to the region where the electric field intensity I is high at the edge portion of the opening.

  On the other hand, as described above, as the plasmon antenna 22 having the nanometer-size opening 22A for generating circularly polarized light inside the bit carrier 15 on the bit patterned medium 10, the above-described FIGS. The four-fold symmetric aperture antenna shown in FIG. 1, that is, a cross-shaped opening 22A in which rectangles having a long side length L and a short side length W are orthogonal to each other is used as a silver (Ag) plate 22B. In the simulation model of the cross aperture antenna provided in FIG. 1, L = 150 nm, W = 20 nm, incident light is incident in the + Z-axis direction, circularly polarized light having a wavelength λ = 780 nm, and the intensity distribution is a central peak electric field of 1 V / m. In a simulation model with a Gaussian distribution and a medium-antenna distance FH = 5 nm, the position of 1 nm on the bit carrier 15 is shown in FIG. Are used to simulate the pointing vector S, the electric field E, the magnetic field H, and the phase difference θ thereof, and the results of evaluating the degree of circular polarization C, the electric field strength I, and the figure of merit F are shown in FIGS. Circularly polarized light can be reliably generated inside, and high-speed and high-density magnetic recording can be performed.

Here, (A), (B), and (C) of FIG. 19 show the degree of circular polarization S, the electric field intensity I, and the figure of merit F in the XZ plane of the simulation model of the cross aperture antenna. 20A and 20B show the degree of circular polarization S in the XZ plane and the direction cosine S _Z / | S in the recording medium direction (+ Z direction) of the simulation model of the cross aperture antenna. Furthermore, FIG. 21 shows the phase difference distribution in the recording medium direction (+ Z direction) and the direction cosine S _Z / | S | at the center of the simulation model of the cross aperture antenna.

22 shows the degree of circular polarization S, the electric field intensity I, and the figure of merit F in the XZ plane of the simulation model of the cross aperture antenna facing the continuous recording medium 250, and facing the continuous recording medium 250. FIG. 23 shows the phase difference distribution in the recording medium direction (+ Z direction) and the direction cosine S _Z / | S | at the center of the simulation model of the cross aperture antenna and the simulation model without the antenna.

As shown in FIGS. 22 and 23, in the simulation model of the cross aperture type antenna facing the continuous recording medium 250 and the simulation model without the antenna, the direction cosine S _Z / | in the recording medium direction (+ Z direction) at the center portion. S | is almost constant and the phase difference distribution is only slightly changed. On the other hand, in the simulation model of the cross aperture antenna facing the bit carrier 15, as shown in FIG. Only in the region, the phase difference distribution in the recording medium direction (+ Z direction) and the direction cosine S _Z / | S | are clearly changed.

  Therefore, in the plasmon antenna 22 having the nanometer-sized opening 22A facing the bit carrier 15 on the bit patterned medium 10 as described above, circularly polarized light can be reliably generated inside the bit carrier 15, and the high speed, High density magnetic recording can be performed.

  That is, in the information recording apparatus 100, the rotationally symmetric opening 22A having a rotational symmetry about the traveling direction of the recording light irradiated with a nanometer size larger than the bit carrier 15 on the bit patterned medium 10 is used. Is irradiated with femtosecond pulsed laser light as the recording light, and excited by the femtosecond pulsed laser light irradiated as the recording light onto the plasmon antenna 22, and the rotationally symmetric aperture 22 </ b> A of the plasmon antenna 22. Due to the interaction between the bit carrier 15 on the bit patterned medium 10 and the rotationally symmetric aperture 22A of the plasmon antenna 22 which is located opposite to the circularly polarized light in the bit carrier 15 to generate direct magnetization. Record information by inversion.

  Conventionally, only recording of a magnetic domain size of about 1 micron can be performed, but recording with a size of several tens of nanometers can be performed by the plasmon antenna 22.

  As described above, according to the present invention, circularly polarized light is locally generated by utilizing the interaction between the nanometer-size opening 22A formed in the plasmon antenna 22 and the recording medium particle 15, and information is obtained by direct magnetization reversal. By recording this, it is possible to simultaneously realize high speed and high density.

  In the information recording apparatus 100 according to the embodiment of the present invention described above, a cross-shaped aperture antenna is used as the plasmon antenna 22 having the nanometer-size aperture 22A facing the bit carrier 15 on the bit patterned medium 10 as described above. That is, although a 4-fold symmetrical aperture antenna is used, in principle, any antenna having a 2-fold symmetry with the traveling direction of the irradiated light as an axis may be used.

  Further, by utilizing the interaction between the nanometer-size opening 22A formed in the plasmon antenna 22 and the recording medium particle 15, elliptically polarized light is locally generated and information is recorded on the recording medium particle 15 by direct magnetization reversal. The plasmon antenna 22 only needs to have a shape having substantially rotational symmetry about the traveling direction of the irradiated light.

  Moreover, a short pulse laser beam can be used for the light irradiated to the plasmon antenna 22.

  In the information recording apparatus 100, information is recorded for each bit by the plasmon antenna 22 having the aperture 22A of nanometer size with respect to the bit carrier 15 on the bit patterned medium 10, but the information is recorded in the insulating matrix. Information may be recorded by the plasmon antenna 22 on fine metal particles of a granular structure recording medium in which nanoscale fine metal particles are dispersed.

  In this case, among the plurality of fine metal particles of the granular structure recording medium existing in the region of the opening 22A of the plasmon antenna 22, the wavelength λ irradiated to the nanometer-size opening 22A of the plasmon antenna 22 is 780 nm. Excited by the femtosecond pulsed laser beam, circularly polarized light is generated in the resonated fine metal particles, and information is recorded.

  In addition, in order to increase the electric field strength locally at the center of the simulation model of the cross aperture antenna, the cross aperture having a shape as shown in FIGS. For a simulation model of a cross aperture antenna having a FDTD method (Finite-difference time-domain method; FDTD method), “Poynting” manufactured by Fujitsu, which is a commercially available general-purpose three-dimensional electromagnetic analysis software, is used. When the electromagnetic field simulation near the aperture antenna was performed, the following results were obtained.

In this simulation model, incident light is incident in the + Z axis direction, circularly polarized light having a wavelength λ = 780 nm, a Gaussian distribution with an intensity distribution of a central peak electric field of 1 V / m, and a Gaussian radius of 780 nm (Intensity = 1 / e ² ). , A cross in which the minimum cell size is 0.5 × 0.5 × 0.5 nm ³ , the long side length L = 160 nm, the short side minimum width W1 = 20 nm, and the maximum width W2 = 60 nm. A cross aperture antenna simulation model in which a cross aperture 122A is provided on a square silver (Ag) plate 122B of 2000 nm × 2000 nm is formed into a matrix with Co recording medium particles 150 having a diameter of 15 nm separated by 10 nm. It was made to oppose the arranged recording medium.

(A), (B), and (C) of FIG. 25 show the degree of circular polarization S ′ in the XZ plane of the simulation model of the cross aperture antenna and the direction cosine S _Z / of the recording medium direction (+ Z direction). | S | and electric field strength I ′ are shown.

In the simulation model of the cross aperture antenna, the circular polarization degree S ′ in the XZ plane when the incident circularly polarized light is reversed, the direction cosine S _Z / | S | in the recording medium direction (+ Z direction), The electric field strength I ′ is shown in FIGS. 26 (A), (B), and (C).

In the simulation model of the cross aperture antenna, the electric field intensity I ′ of the recording medium particles 150 located in the periphery was 0.21 [(V / m) ₂ ], whereas the recording medium positioned in the center. The electric field intensity I ′ in the particle 150 is 0.6 [(V / m) ₂ ], and the electric field intensity can be locally increased in the central portion of the simulation model of the cross aperture antenna.

  In the above-described embodiment of the present invention, the information recording apparatus including the information recording head to which the present invention is applied has been described. However, the present invention is not limited to the above-described embodiment.

  That is, according to the present invention, since the magnetization direction of particles can be changed by laser light, a device that utilizes a change in magnetic interaction between magnetic bodies by contacting another magnetic body with a magnetic body that changes the magnetization direction. For example, a magnetoresistive element, a magnetic transistor, a magnetic switch, or the like can be an optical device that can be controlled by laser light irradiation.

  Here, FIGS. 27A and 27B show a configuration example of a magnetoresistive element that is an optical device that can be controlled by laser light irradiation.

  The magnetoresistive element 200 includes a cylindrical magnetic particle part 210 whose magnetization direction is changed by being irradiated with laser light, and two magnetic body parts 221 and 222 in contact with the cylindrical magnetic particle part 210 (which are magnetized). The end of the cylindrical magnetic particle 210 is positioned at the center of the cross opening 230A of the plasmon antenna 230.

  That is, the magnetoresistive element 200 is an optical device having a function of changing a magnetic effect by laser light irradiation, and includes a magnetic particle portion 210 whose magnetization direction is changed by the laser light irradiation, and the magnetic particle portion. Two magnetic body portions 221 and 222 disposed in contact with 210, and a plasmon antenna 230 having a substantially rotational symmetry about the traveling direction of laser light irradiated with a size larger than that of the magnetic particle portion 210. With.

  The magnetoresistive element 200 is excited by the laser light applied to the plasmon antenna 230, and interacts with the magnetic particle part 210 positioned opposite the plasmon antenna 230 and the plasmon antenna 230. Then, circularly or elliptically polarized light is generated in the magnetic particle part 210 and the magnetic action of the magnetic body parts 221 and 222 disposed in contact with the magnetic particle part 210 is changed by direct magnetization reversal. When the magnetization direction of the cylindrical magnetic particle part 210 is changed by the irradiation of the laser beam, the magnetization direction of the two magnetic body parts 221 and 222 in contact therewith (the magnetization direction is fixed upward) When the magnetization direction of the cylindrical particle part 210 is directed upward, the resistance between AB is small, and the resistance between AB is large in the reverse direction (there may be the opposite depending on the magnetic material). As described above, since the magnetic interaction with the outside can be varied by changing the magnetization direction, the method of the present invention can be used for high-speed operation of any magnetic device that exhibits a function by reversing the magnetization.

10 bit patterned media,
15 bit carrier,
20 Information recording head,
21 light source,
22A rotationally symmetric opening 22B silver (Ag) plate,
30 detector,
40 control unit,
100 information recording device,
200 magnetoresistive element,
210 cylindrical magnetic particle part,
221, 222 magnetic body part,
230 Plasmon Antenna

Claims (11)

An information recording head for recording information with a laser beam on a recording medium having a recording layer in which recording medium particles are dispersed,
A plasmon antenna having a substantially rotational symmetry with the traveling direction of the recording light irradiated in a larger size than the recording medium particles dispersed in the recording layer of the recording medium as an axis;
The interaction between the plasmon antenna and recording medium particles that are excited by the laser light applied to the plasmon antenna as the recording light and are dispersed in the recording layer of the recording medium that is positioned facing the plasmon antenna Thus, the information recording head is characterized in that circularly or elliptically polarized light is generated in the recording medium particles and information is directly recorded by magnetization reversal.   2. The information recording head according to claim 1, wherein the rotational symmetry of the plasmon antenna is four-fold symmetric. A recording medium having a recording layer in which recording medium particles are dispersed;
A plasmon antenna having a substantially rotational symmetry about the traveling direction of the recording light irradiated with a size larger than the upper recording medium particles;
A light source that emits laser light as the recording light to the plasmon antenna;
The interaction between the plasmon antenna and recording medium particles that are excited by the laser light applied to the plasmon antenna as the recording light and are dispersed in the recording layer of the recording medium that is positioned facing the plasmon antenna Thus, information is recorded by generating circularly polarized light or elliptically polarized light in the recording medium particles and directly recording information by magnetization reversal.   4. The information recording apparatus according to claim 3, wherein the rotational symmetry of the plasmon antenna is four-fold symmetric.   4. The information recording apparatus according to claim 3, wherein the light source irradiates a short pulse laser beam.   4. The information recording apparatus according to claim 3, wherein the recording medium is a bit patterned medium in which a plurality of bit carriers for recording one magnetic particle as one bit are arranged.   4. The information recording apparatus according to claim 3, wherein the recording medium is a granular structure recording medium in which nanoscale fine metal particles are dispersed in an insulating matrix. An information recording method for recording information with a laser beam on a recording medium having a recording layer in which recording medium particles are dispersed,
Irradiating a laser beam as the recording light onto a plasmon antenna having a rotational symmetry with the traveling direction of the recording light irradiated in a size larger than the recording medium particles as an axis;
The interaction between the plasmon antenna and recording medium particles that are excited by the laser light applied to the plasmon antenna as the recording light and are dispersed in the recording layer of the recording medium that is positioned facing the plasmon antenna Thus, information is recorded by generating circularly-polarized light or elliptically-polarized light in the recording medium particles, and recording information by direct magnetization reversal.   9. The information recording method according to claim 8, wherein the plasmon antenna having a four-fold symmetry is irradiated with a short pulse laser beam as the recording light. An optical device having a function of changing a magnetic effect by laser light irradiation,
A magnetic particle portion whose magnetization direction is changed by irradiation with the laser beam;
At least one magnetic body portion disposed in contact with the magnetic particle portion;
A plasmon antenna having a substantially rotational symmetry with the traveling direction of laser light irradiated with a size larger than the magnetic particle portion as an axis, and
Generates circularly or elliptically polarized light in the magnetic particle part by the interaction between the plasmon antenna and the magnetic particle part that is excited by the laser light irradiated to the plasmon antenna and is opposed to the plasmon antenna. An optical device characterized in that the magnetic action of the magnetic part arranged in contact with the magnetic particle part is changed by direct magnetization reversal. Comprising two magnetic parts arranged in contact with the magnetic particle part,
Due to the interaction between the magnetic particle part and the plasmon antenna, circularly polarized light or elliptically polarized light is generated in the magnetic particle part, and direct magnetization reversal between two magnetic material parts arranged in contact with the magnetic particle part The optical device according to claim 10, wherein the magnetoresistance of the optical device is changed.

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