We have investigated the fabrication, structural and magnetic properties of L1₂-type CrPt₃(111) film by annealing Cr(110)/Pt(111) superlattice. L1₂-type CrPt₃(111) films are successfully fabricated above the annealing temperature of 1173 K. The order parameter is altered by changing the annealing temperature and the Pt thickness in Cr/Pt superlattice in keeping Cr thickness. While the Cr/Pt superlattice is non-magnetic, L1₂-type CrPt₃ film shows the magnetic hysteresis at room temperature, and the magnetically ordered L1₂-type CrPt₃(111) film possesses the perpendicular magnetic anisotropy. The perpendicular magnetic anisotropy energy increases with increasing order parameter S, and the effective magnetic anisotropy energy K of 3.3×10⁶ erg/cc is obtained at S∼1.0. The magnetic domain energy σ_W is estimated from domain pattern at remanent state. For the sample with S∼1.0, σ_W of 1.49 erg/cm² is obtained.

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  We have investigated the relationship between the crystal structure and the magnetic anisotropy constant of epitaxially grown Fe/Co multilayers (ML). The Fe/Co ML grown on a Ag (100) underlayer at ambient temperature exhibits body centered cubic (bcc) structure with (100) orientation for the stacking period λ less than 15 nm. The saturation field along the film normal is much larger than the demagnetization field 4πM_s, indicating negatively large magnetic anisotropy K_u. The negative K_u takes the peak value as large as −1×10⁷ erg/cc at λ = 0.75 nm. This behavior of K_u against λ is very similar to that reported for Fe/Co (110) polycrystalline ML [Vas'ko et al., Appl. Phys. Lett. 89, 092592 (2006)]. Moreover, slight lattice distortion is observed, but the magnetoelastic contribution is much smaller than the negative K_u. These results lead to the conclusion that the negative K_u of Fe/Co ML is attributable to the interfacial magnetic anisotropy with weak crystal orientation dependence.

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  The tunnel magnetoresistance (TMR) effects of granular films employing CoFeAlSi (CFAS) were investigated. The granular films were composed of MgO buffer, CFAS, and protective MgO layers. A structural change from continuous to granular structures was clearly seen in the resistivity, depending on the nominal thickness of CFAS. The samples prepared on the heated substrate showed large MR ratios, with a maximum MR ratio of 5.5% for a CFAS thickness of 2.0 nm. From the X-ray photoelectron spectroscopy depth profile, Fe was preferentially oxidized on the surface of granules, although Co was not. TEM micrographs showed relatively uniform granules, with a diameter of 3.0-5.0 nm, for the samples prepared on a substrate heated at 200°C. However, an L2₁ ordered structure was not confirmed due to low substrate temperature.

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  Magnetic properties of amorphous TbFeCo magnetic film on periodic nanodot pattern were examined. Cross sectional TEM image revealed the magnetic film deposited on a nanodot pattern with two dimensional periodicity of around 28 nm had columnar structure on the convexity portion. Measured magnetic properties and magnetic force microscope images indicated miniaturization of the magnetic domain attributed to the reduction of magnetic exchange coupling between the columns.

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  Magnetization reversal time in ferrimagnetic material is compared with that in ferromagnetic material. Since ferromagnetic material is in a state of underdamping, the reversal time is relatively long. A formula for reversal time in ferrimagnetic material is deduced under the assumption that the effective Gilbert damping parameter α_eff is inversely proportional to the net angular momentum. In the case of g₁=g₂, where g₁ and g₂ are the g-factors of the first and second sublattices, respectively, the reversal time in ferrimagnetic material is much shorter than that in ferromagnetic material because α_eff in ferrimagnetic material can be adjusted so that α_eff=1. Furthermore, in the case of g₁≠g₂, the reversal time becomes much shorter than that when g₁=g₂ because a large net magnetization and small net angular momentum can be realized.

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  We have investigated the fabrication of α-Cr₂O₃(0001) thin film on a Au(111) surface and the effect of the antiferromagnetic feature of α-Cr₂O₃(0001) on the magnetic properties of ultrathin Co film on α-Cr₂O₃(0001). Highly oriented α-Cr₂O₃(0001) thin film is fabricated by oxidizing Cr(110) thin film grown on a Au(111) surface. Upon the oxidization of threefold symmetric Cr(110) thin film, the α-Cr₂O₃(0001) thin film is produced. On α-Cr₂O₃(0001) thin film, ultrathin Co film is epitaxially grown at 473 K to form fcc-Co(111) film. The antiferromagnetic feature of α-Cr₂O₃ affects the magnetic properties of the ultrathin Co film. Exchange bias is only observed when the magnetic field is applied perpendicular to the film surface, i.e., the direction parallel to the Cr spin. Additionally, in the temperature dependence of magnetization, the clear signature of a Néel temperature of approximately 300 K is observed. The obtained results indicate the collinear coupling of Co and Cr spins.

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  We have investigated the effective synthesis of Pyrococcus furious virus like particle (PfV) and the integration of Ni²⁺ ions with PfV. Application of Isopropyl-β-D-1-thiogalactopyranoside (IPTG) during incubation of P. furious causes the marked improvement of yield of P. furious. Using the synthesized P. furious, the spherical structure of PfV is successfully obtained. Concerning magnetism, the native PfV shows the diamagnetic properties. On the contrary, after the integration with Ni²⁺ ions, the paramagnetic behavior appears, namely the non-saturated M-H curve with zero remanence and coercivity, and Curie law like M-T curve. The obvious changes in the magnetic properties indicate that the Ni²⁺ ions are successfully integrated with PfVs.

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  The play back system of digital video signal which transfers the information stored in magnetic tapes to garnet film and reads out it magneto-optically is being developed. To put the system to practical use, it is expected that the signal recorded with wavelength of shorter than 0.8μm is read out with sufficient carrier-to-noise ratio (CNR). We confirmed that it was possible to read out a signal with wavelength of 0.77μm experimentally and analytically as well. To achieve a good CNR we measured spectra of readout signal by using a transfer readout exerciser. On the bases of a series of experiments, we found that dominant noise was polarized noise due to granularity of magnetic tape. By elongating the readout spot in the direction of recorded track width by three times that of normal, improvement of CNR more than 10 dB was obtained.

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  To obtain enhancement and wavelength tuning of the magneto-optical (MO) response associated with the localized surface plasmon resonance (LSPR), bismuth-substituted yttrium iron garnet (Bi:YIG) composite films with Ag particles and Au-Ag alloy particles were studied. The Bi:YIG composite film with Ag particles did not show any enhancement of Faraday rotation. On the contrary, the Bi:YIG composite films with Au-Ag particles exhibited the enhancement of the MO response for different wavelengths of LSPR. We observed the enhanced Faraday rotation for the Bi:YIG/Au-Ag composite films with volume ratios of Ag up to 0.6. In addition, when changing the volume ratio of Ag, the peak of rotation shifted to short wavelengths. Disappearance of enhancement for the Bi:YIG/Ag composite film can be addressed to modifying the interfacial medium between the MO host and Ag. Since chemically active Ag particles can form nonmagnetic Ag compound shells separating Bi:YIG and the plasmonic subsystem, the LSPR of Ag particles did not affect the MO response. The Au-Ag alloy particles were chemically stable in the Bi:YIG/Au-Ag composite films.

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  A new type of magnetic field optical sensor with a diode-pumped solid-state microchip laser was studied. It was found that use of the self-mixing laser intensity modulation method combined with an acousto-optic frequency shift enabled the detection of Faraday signals in an extremely weak feedback field. Through experiments using an Nd:YVO₄ microchip laser and a YIG crystal as a Faraday element, modulation signals proportional to the applied magnetic field were obtained in the very weak amplitude feedback region of 10^-6.

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  Bismuth-substituted yttrium iron garnet (Bi:YIG)-based magnetophotonic crystals (MPCs) with 2D structure were fabricated using autocloning of various patterns. We studied structural properties of these MPCs and evaluated their magneto-optical responses. Enhanced Faraday rotation of the same sign as that for conventional Bi:YIG films and of the opposite sign was observed for 2D patterned Bi:YIG films fabricated on top of opal films.

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  In order to study the low temperature process to fabricate (001) oriented FePt granular structure, FePt-Ag and FePt-MgO films were fabricated by the repetition process of deposition of Fe₄₀Pt₄₀Ag₂₀ (0.83 nm) or Fe₄₀Pt₄₀(MgO)₂₀ (0.83 nm) alloy layer and subsequent annealing at T_a = 200°C−400°C. The FePt-Ag film showed (001) oriented structure together with rather high ordering parameter of 0.5 even at a low process temperature of 250 °C. The ordering parameter of FePt-Ag was found to be much higher than that of FePt-MgO. The FePt-Ag prepared by the repetition process at 250 °C had well isolated grain structure with diameters of several nm to several tens nm, and showed a large uniaxial anisotropy of 1.0 x 10⁷ erg/cc. The application of the repetition process and Ag addition into FePt was found to be quite effective to fabricate well isolated L1₀ ordered FePt granular structure at a low process temperature.

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  We investigate the dynamics of the magnetization reversal in single Pt/Co(0.5 nm)/Pt nano-discs with diameter 130 nm, fabricated by He⁺ ion irradiation. They exhibit a very narrow distribution of small switching fields and a perpendicular magnetic anisotropy. In spite of their small magnetic volume, thermally activated magnetization reversal cannot be interpreted within the usual Néel-Brown model. Non-coherent magnetization reversal proceeds here by fast nucleation at nano-disc borders and rather slow wall motion towards their center. Dynamics are perfectly accounted for by a 2D-confined droplet model, involving the wall energy rather than the anisotropy energy. On the other hand, the blocking temperature for these nano-discs is well described by the coherent spin reversal model.

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  We propose a new configuration for an optical thermally assisted magnetic recording (TAMR) head. The configuration allows us to place an optical near-field spot close to a magnetic write pole. In this system, we use a Focusing Waveguide integrated into a flying slider and a metal plasmon antenna attached to the bottom surface of the waveguide. With the proposed configuration, the intensity of the optical near-field spot peaks when the optical near-field spot is placed at the clad of the Focusing Waveguide. As a result, we can decrease the distance between the optical heating spot and the magnetic write pole. We present some simulation results of optical near-field generation. The distance between the near-field spot and the magnetic pole is decreased to 120 nm. This configuration is useful in decreasing the time lag between optical heating and magnetic writing.

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  In this study, FePt or FeCuPt particles were fabricated by rapid thermal annealing method on two kinds of nano-structured substrates. In order to increase areal density of particles N_p, nano-structred substrate was utilized. Two different kinds of nano-structured substrates were successfully prepared. One of them is a Nano-Dent Array (NDA) at the surface of SiO₂ layer which is including closed packed nano-pores with periodicity of 14 nm was prepared by the polymer micelles technique and the other is Self-Assembled spherical small Silica Particles (SASP) with diameter of 18 nm was fabricated on Si substrates by the dip coating method. By utilizing NDA, average diameter D_a of FeCuPt particles was successfully reduced and N_p was drastically increased (D_a = 4.8 nm, N_p = 6.6 T particles/inch² at the case of initially deposited Pt/Fe/Cu thickness is 1.25 nm) comparing to use of flat SiO₂/Si substrate. Although FeCuPt particles was tended to grew up on convex part of NDA, the particles of over 10nm diameter that is near the same size with the diameter of nano-dent tend to grow up such ignoring of the nano-dent structures. On the other hand, preparing FePt on SASP under the condition of the resulted D_a = 15 nm (initially deposited Pt/Fe thickness is 3.75 nm) which almost no effect was observed on NDA, N_p (= 0.76 T particles/inch²) was four times increased compared with preparing on flat SiO₂/Si substrate. It was found that starting from thinner initial bi-layer thickness of 1.88 nm D_a decreased to around 5.1 nm and N_p increased up to about 5.4 T particles/inch². Furthermore, we observed the effect to structural and magnetic property of TbFeCo film by SASP substrate. Columnar structure was appeared and the magnetic Coercivity of TbFeCo continuous film was enhanced.

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  We developed a stacked volumetric optical disks (SVOD) system to realize a data capacity of over 1 TB in a cartridge. To increase the read and write speed of the SVOD system, the mechanical performance characteristics of the 92-μm-thick thin optical disk stored in the SVOD cartridge were investigated by combining the magnetic amplifying magneto-optical system (MAMMOS) structure and 15000 rpm ultra-high-speed rotation. The minimum 40 nm mark length has already been reached with MAMMOS recording. This corresponds to 100 GB per disk of CD size. The thin optical disk can be rotated at over 10000 rpm because thin optical disks are flexible, and shatter rarely in comparison with conventional 1.2-mm-thick optical disks. As a result of the study, the mechanical performance characteristics were found to be acceptable for practical use. Therefore, the maximum data transfer rate can be upgraded to more than 2 Gbps by using a combination of thin optical disks, magneto-optical (MO) recording, and 15000 rpm ultrahigh-speed rotation.

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  This research applied thermally assisted magnetic recording to analyze both temperature distributions and temperature time transitions of isolated columnar structured media. It was clarified how a higher thermal resolution could be achieved using columnar structured media compared with continuous film media. With the application of a plasmon antenna, bit-patterned media achieved a writing temperature of more than 10 times higher than that of conventional media. Temperatures of adjacent columns strongly depend on the arrangement and the shape of a plasmon antenna.

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  Tb-Fe-Co, an RE-TM alloy, is a promising material for perpendicular magnetic CPP-GMR devices. Because the spontaneous magnetization of RE-TM alloy can be controlled by its composition, the magnetic field generated from the pinned layer can be reduced by using a Tb-Fe-Co alloy film for the pinned layer. However, Tb-Fe-Co oxidizes easily. In this study, we applied a Si-N insulating layer to a CPP-GMR device in place of a SiO₂ protective layer and successfully improved the magnetic characteristics of the Tb-Fe-Co pinned layer.

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  Spatial light modulator (SLM) is a real-time programmable device for modifying amplitude, phase or polarization of optical wave front by electrically controlled signals. Various types of SLMs with pixel arrays, such as a liquid crystal SLM, have been developed. Recently, SLMs have received much attention as a light modulator in holographic data storage which requires high speed SLMs for ensuring the high data transfer rate. In this field, the application of a magneto-optic SLM (MOSLM) is highly expected because of extremely fast pixel switching speed. The conventional MOSLM used a single crystal garnet with perpendicular magnetic anisotropy to switch as a binary depending on up and down magnetization. However, for an analog modulation in our concept, the direction of magnetization is gradually changed to in-plane direction, because the modulation is depending on the magnetization direction of the garnet film. A voltage driven MOSLM for analog modulation is developed using magnetostriction effect. Moreover, the MOSLM with a structure of a magnetophotonic crystal (MPC) is fabricated for the large enhancement of magneto-optical response. This report is about a current development of MOSLMs with magnetophonic crystal driven by a voltage.

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