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Hologram memory is a promising data storage technology with a high recording density and fast data-transfer rate. Magnetic garnet media such as Bi1.3Dy0.85Y0.85Fe3.8Al1.2O12 (substituted rare-earth iron garnet, SRIG) films have advantages of rewritability and unnecessity of shielding. The diffraction efficiency of these garnet films, however, is not sufficient to apply to storage devices. In this paper, we proposed a use of magnetophotonic crystals (MPC) as hologram media and calculated their diffraction efficiency. The results indicated that MPC media showed a high diffraction efficiency compared with single SRIG films, and especially the MPC medium with the structure of substituted gadolinium gallium garnet substrate / (Ta2O5 / SiO2) 2 / SRIG / (SiO2 / Ta2O5) 2 with the SRIG thickness of 3.88 m exhibited the diffraction efficiency of 0.36%. A large Faraday rotation angle and deep magnetic hologram fringe originated from the localization of light results in such a high diffraction efficiency.

Dual-cavity magnetophotonic crystals (MPCs) based on bismuth-substituted yttrium iron garnet (Bi:YIG) have been fabricated by a bonding method, and their structural, optical and magneto-optical properties have been studied. Identical structure of bonded fractions revealed the existence of the Fabri-Perot resonances in transmission spectra of single- and dual-cavity MPCs and corresponding enhancement of the Faraday rotation. However, the bonding interface was found to be unstable because of the bonding surfaces' roughness introduced by crystallization of Bi:YIG.

We fabricated magnetophotonic crystals (MPCs) used in electric field driven magneto-optical spatial light modulators (e-MOSLMs) with a paramagnetic garnet, which is transparent in the blue wavelength region and has a sufficient Faraday rotation angle for several applications including hologram data storage, three-dimensional displays, and optical correlators. The e-MOSLM is composed of two dielectric mirrors and one defect layer comprising magneto-optic (MO) material and electro-optic (EO) material, which controls the localized wavelength due to the change in the refractive index. The e-MOSLM utilizing MPCs allows us to use thin film paramagnetic materials, i.e., a terbium gallium garnet (TGG) and a terbium aluminum garnet (TAG), instead of a rare-earth iron garnet (RIG) because the direction of magnetization does not need to be controlled in the MO layer. We fabricated TGG thin films and MPCs with the structure of a SGGG substrate/(Ta2O5/SiO2)6/TGG/(SiO2/Ta2O5)6 by rf-magnetron sputtering. The sample produced localized peaks in the photonic band gap of the transmission spectra and an enhanced Faraday rotation angle. These results indicate that e-MOSLMs comprising an MPC with a TGG defect layer can be useful devices at the blue wavelength.

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.

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.

The magneto-optic spatial light modulator (MOSLM) can modulate amplitude, phase, and polarization of optical wave front at high speed. However, past MOSLM requires large driving current. To overcome the disadvantage, we have developed the MOSLM with PZT layer driven by electric field and external magnetic field. The effective structure of the voltage-driven MOSLM was also investigated using finite element simulation. A magneto photonic crystal(MPC), which consists of dielectric mirror and magnetic defect layer, can largely enhance MO effect. The stress distribution calculation of MPC structure with good stress distribution and a large Faraday rotation was done based on a structure of a thin MO film.

By using a ferrite plating technique and stereolithography, we fabricated the medical magnetic micro-machines that plated ferrites on a spiral-structured resinous substrate. We plated a magnetite (Fe3O4) film with good biocompatibility and CoxFe3-xO4 films (CO0.39Fe2.61O4 or Co0.45Fe2.55O4) having large coercive force onto template bodies at 90°C for 5-8 hours, and fabricated solid-state-based ferrite-coated micro-machines with biocompatibility and light mass density. All the micro-machines were able to swim in water when an external rotational magnetic field was applied.

The swimming properties of a magnetic micro-machine with a spiral structure were examined experimentally and theoretically under very low Reynolds number conditions. It was demonstrated that the micro-machine could swim in a highly viscous fluid with a Reynolds number of 10-7. This result suggests that the micro-machine has a great potential for medical applications. It was found that the optimum blade shape of the micro-machine varied with the Reynolds number condition.

A remote temperature sensing system was investigated for use, local such as inside the human body. The system was divided into a magnetic generating part, temperature sensing and temperature information generating part, and temperature information receiving part. A ferrite having a low Curie temperature was used in the temperature sensing part. To receive and transmit the temperature information effectively, LC resonance circuits were used in the system. The resonance frequency of 145 kHz to 220 kHz was varied in the range of 58°C to 66°C. From this experiment, we determined that temperature could be measured at the local site using this system.

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.

The fundamental swimming properties of spiral-type magnetic micro-machines were investigated in detail by constructing four micro-machines with different structures. These micro-machines are able to swim in various liquids with kinematic viscosities ranging from 1.37 to 1000 mm2/s. This result suggests that the micro-machines have potential medical uses. In particular, they can swim against the stream in a liquid whose the velocity is comparable to the that of venous blood.

Amorphous FeCoSiB films with high saturation magnetostriction and excellent soft magnetic properties were studied to determine their strain sensitivity. The films were subjected to strain by bending of their substrates, which caused a change in the magnetic anisotropy of films via magnetoelastic coupling. The films exhibited a figure of merit F ≡ (θμ/θe)/μ (change in film permeability μ per unit of strain e) of 1.2 × 105, which is comparable to that of amorphous ribbons. To study the use of the magnetostrictive films as strain sensor elements, we prepared meander-patterned films by means of the photolithography and ion milling processes. The impedance change in the patterned films when strain was applied was measured in the frequency range from 1 MHz to 1 GHz. Reflecting the large value of F, the high-frequency impedance of the films was changed considerably: a change in impedance of 46% was observed at 100 MHz when a strain of 300 × 10-6 was applied. It is also demonstrated that, by using the strain-dependent impedance, a small strain of 1 × 10-7 can be detected by means of the film pattern.

The dysprosium substituted yttrium iron garnet (Dy:YIG) film was investigated because of high magnetstriction for operating voltage driven type magneto-optic spatial light modulators (V-MOSLMs). The fabricated Dy:YIG film had magnetostriction of 3.5 ppm, soft magnetic property, transmittance of 47 % and faraday rotation of -2.7 deg./μm at 532 nm wavelength. Furthermore, a reflection type one dimensional magneto photonic crystal (1D-MPC) by using the Dy:YIG film as a defect layer was fabricated for enhancement of Kerr rotation. In the case of the defect layer of 147 nm thick, a Kerr rotation angle was 15 times higher than the single layer at localized wavelength.

We demonstrate a newly developed magneto-photonic crystal (MPC) based magneto-optic spatial light modulator (MOSLM) which was designed to enhance the performance of a conventional MOSLM, and describe the preparation and fundamental properties of it. By introduction of MPC, the magneto-optical property of MOSLM was improved, and as driving properties, the saturation of brightness was shown around ±1 kOe and the change occurred from about ±300 Oe by external magnetic field. Also, we conformed that Kerr rotation angle of this device was varied by applying voltage to PZT film. The change of each pixel by applying voltage, however, could not be detected because of the small variation of brightness.

We have studied propagation of magnetostatic surface waves in yttrium iron garnet films with attached 1D periodic arrays of metal strips. For different experimental geometries and different designs of 1D periodic arrays of metal strips, propagation spectra of magnetostatic surface waves were measured and analyzed. We have shown a way to control propagation characteristics of magnetostatic surface waves by changing of electrical contact between periodic metal strips.

To obtain amorphous FeB-plated films with soft magnetization, the effect of a combined complex agent of potassium sodium tartrate (KNaC4H4O6 · 4H2O) and ammonium sulfate ( (NH4)2SO4) on the film properties was investigated. Soft magnetic films with coercivities of less than 4 Oe were obtained by using a bath composition of KNaC4H4O6 · 4H2O = 600mmol/L and (NH4)2SO4 = 80mmol/L. These soft films also exhibited large magnetostriction of 26 × 10-6, suggesting that the use of the combined complex agent is very effective for obtaining FeB amorphous films that have soft magnetic properties and large magnetostriction simultaneously. Change in composition of films along their thicknesses is considered to be responsible for the magnetic softening of FeB-plated films.

Magneto-electric (ME) elements were constructed by combining piezoelectric materials and magnetostrictive films. The fundamental properties of elements were studied, to determine whether the elements exhibit any considerable ME effect at room temperature. The elements had a hybrid structure, in which thin soft glass substrates with highly magnetostrictive amorphous FeCoSiB films were bonded on PZT piezoelectric substrates. When a dc voltage was applied to an element, large changes in the magnetic properties of the FeCoSiB film were observed: for example, when a dc voltage of between -200 V and +200 V was applied, the change in magnetic permeability of the film reached more than 1680%. These unique characteristics of the present ME elements are considered to be very attractive for constructing novel types of micromagnetic devices.

A magneto-optic spatial light modulator (MOSLM) driven by an electric field was fabricated, which is multiferroic device with magneto-optical garnet layer and piezoelectric PZT one. To control the direction of magnetization of the garnet layer, a stress field induced by PZT film was applied to the garnet layer. With an external magnetic field, the pixels of the MOSLM were switched. The driving current required for the magnetization switching was remarkably reduced to 500 nA, whose value was less than 1% of a driving current of the conventional current-driven MOSLM.

A magneto optic spatial light modulator (MO-SLM) for multiple-tone expression was fabricated by using in-plane magnetization of garnet film. By using Al substituted Bi:YIG film, magnetization curve was modified to suitable for multiple tone expression. Changing a driving current from 0 to 28 mA, we were able to change brightness of pixels in the line.

Bismuth-substituted yttrium iron garnet (Bi:YIG, Bi0.5Y2.5Fe5O12) films have been deposited with aerosol deposition method. We investigated the deposition rate, crystallinity, magnetic and optical properties dependent on carrier gas flow rate (0.5 L/min ∼ 8 L/min) and annealing temperature. With increasing annealing temperature, the crystallinity of Bi:YIG film was improved and the saturation magnetization increased to reach to 1.1 kG at 800°C. The magneto-optical effect, Faraday rotation, increased to 1.4 deg/μm by annealing at 700°C around the wavelength of 0.5 μm. The optical transmittance of the Bi:YIG film was also improved in visible region.

By using the "glycol gel process" utilizing nitrates of bismuth, yttrium and iron dissolved in ethylene glycol as the liquid precursor, single phase bismuth-substituted yttriulll iron garnet (Y3-xBixFe5O12) polycrystalline films with the amount of bismuth substitution x up to 2.5 were prepared by spin-on process on glass substrates, where garnet films with larger x were grown by repetitive gel-coating on thin garnet layer with x=1.5. In addition, the effect of copper or zinc ion substitution on magnetic and magneto-optical properties was examined for films with the chemical formula of Y2BiFe5-yMyO12, where M=Cu2+. or Zn2+

Magneto-optical Faraday effect of cobalt nano-clusters oriented uniaxially in a transparent matrix was studied. The experimental results showed that the oriented films were good polarizing plates with very unique MO properties which varied depending on the geometry of film structures and the polarization of incident lights. Numerical analysis revealed that the MO properties originated in the mode conversion of lights from TE to TM, arising from the magnetic and optical uniaxial anisotropies.

Propagation properties of fundamental magnetoelastic waves (MEWs) in a highly magnetostrictive slab have been studied. Analysis and experiment show that there exist three fundamental MEWs: Lamb extensional-type, Lamb flexural-type and SH-type MEWseven in a single homogeneous magnetic slab. The results reveal that the propagation properties of MEWs are determined by not only the magnetic parameters such as the magnetoelastic coupling constant but also by the geometrical ratio of the thickness to the drive frequency. The analysis suggests that in order to realize large velocity change in MEWs with a small field the easy axis direction should be changed according to whether the Lamb-type or the SH-type MEW is used. The SH-type MEW exhibits distinct frequency dispersion which is not observed in the elastic SH-wave in a non-magnetic slab.

Magnetoelastic waves (MEWs) propagating in a thin conductive magnetostrictive slab were investigated theoretically taking account of the micro-eddy current contribution. The analysis was performed under the assumption that the medium is amorphous (isotropic elasticity) but has a uniaxial magnetic anisotropy in the slab plane. MEWs in this configuration are three fundamental modes: Lamb-type wave of the extensional mode (EMEW), SH-type wave (SMEW) and Lamb-type wave of the flexural mode (FMEW). The microeddy current crucially affected the propagation properties, thereby increasing the propagation loss as well as decreasing the controllable MEW velocity with external magnetic field. The amounts of these quantities also varied depending strongly on the anisotropy orientation β for the above three wave modes, because the degree of coupling between the magnetization and the lattice through magnetoelastic interaction is different in each mode. The present analysis revealed that SMEW with β=45° is the most favorable for delay line application.