As efficient current induced magnetization switching schemes, thermally assisted spin transfer torque (STT) switching, spin orbit torque (SOT) switching of rare-earth transition metal films, and electric-field assisted SOT switching were briefly reviewed. For thermally assisted STT switching, hybrid memory layer with a low Curie temperature (T_C) and high T_C layers were found to be effective to reduce the critical current density J_c without sacrificing the thermal stability Δ at room temperature. In SOT switching of GdFeCo, the large SOT was confirmed even at the compensation composition of GdFeCo. In SOT switching of MgO / Co / Pt films, the switching current density J_c was confirmed to be modified around 20% by applying an electric field of 1 V/nm through the insulator film.

Spin-polarized light-emitting diodes (Spin-LED) consisting of ferromagnetic electrodes, an ultra-thin tunneling barrier layers and semiconductor LED structure can emit circularly polarized light (CPL) through radiative recombination of spin-polarized electrons and holes. A lateral-type spin-LED with crystalline AlO_x tunnel barrier layers have been developed for practical applications and have achieved pure CPL emission, electrical helicity control and CPL detection at room temperature. This article reviews recent progress on spin-photonic devices such as spin-LEDs and spin-photodiodes and introduces the applications based on CPL.

Spin dynamics and magnetic characteristics of (YRBi)₃(FeGa)₅O₁₂ thin films fabricated by metal organic decomposition (MOD) method is studied. The magnetic anisotropies of Y_1.5R_0.5Bi₁Fe₄Ga₁O₁₂ (R = Dy, Gd, or Eu) garnet films prepared by the MOD on Gd₃Ga₅O₁₂ (GGG) single crystal substrates were analyzed, and the crystalized phases of the films were also evaluated by X-ray diffraction (XRD). It is found that magnetic anisotropy of the films can be induced by a lattice difference between the film and the substrate, even though the films are made by the MOD. The damping factor of a Y₂Bi₁Fe₅O₁₂ garnet film was measured by ferromagnetic resonance using co-planer waveguide, and the measured damping factor of the Y₂Bi₁Fe₅O₁₂ film made by the MOD on GGG substrate is 0.073. The value, which shows much larger than that of other garnets, must be caused by the less crystallinity and/or the fine structure of the films.

Holographic memory is a strong candidate for next-generation optical storage with high recording densities and data transfer rates, and magnetic hologram memory using a magnetic garnet, as the recording material, is expected to be used as a rewritable and stable storage technology. We succeeded in recording and reconstruction of 2D data in magnetic hologram without error. However, the diffraction efficiency is insufficiently high for actual storage devices. To increase the diffraction efficiency, it is important to record deep magnetic fringes whereas the merging of fringes due to the excess heat near the medium surface generated during the thermomagnetic recording process must be suppressed. To avoid this merge of fringes, we proposed a multi-layered structure in which the magnetic layers are divided by the transparent heat dissipation layers (HDL) to control the heat diffusion. In this study, we propose a simple thermal design method for designing the HDL multilayer structure. Using this model, we designed and fabricated a HDL multilayer medium in which the recording magnetic layers are discrete in the film. The HDL multilayer medium exhibited diffraction efficiency higher than that of the single layer medium, and error-free recording and reconstruction were achieved using the magnetic assist technique.

Pre-annealing process in the metal-organic decomposition (MOD) method for Bi-substituted Nd magnetic garnet films was studied. In this paper, we report on crystallinity and magneto-optical (MO) properties of Nd₂BiFe₄Ga₁O₁₂ and Nd_0.5Bi_2.5Fe₅O₁₂ thin films prepared with pre-annealing temperatures of 250 - 500ºC and annealing temperature of 650ºC. Decomposition process of metal carboxylates in the MOD solutions were investigated by means of FT-IR measurement for pre-annealed thin films. It was found that, good crystallinity and MO property were obtained for the thin films prepared with the pre-annealing temperatures of 350 - 450ºC, in which alkyl group was decomposed, while -COO^- was remained.

All-Optical magnetization Switching (AOS) is one of promising candidate for fast magnetization manipulation. AOS is occurred by a single ultrashort laser pulse irradiation without any external magnetic field. AOS has fundamentally different mechanism from conventional magnetic field driven switching. In this report, we discussed new layered structure for efficient light absorption and ultra-thin film formation in material that induces All-Optical magnetization Switching.

In recent years, a magnetocardiography (MCG) with superconducting quantum interference device with noise level of 50 fT/√ Hz is used for arrhythmia diagnosis. The MCG is usually installed in a multi-layered magnetically shielded room (MSR). In the MCG close to some magnetic noise sources like DC (direct current) electrified railway, the MCG can stably measure the magnetic field by increasing the number of layers of MSR. However, increasing the number of layers in the MSR increases the cost and weight. We developed the method to correct the environmental magnetic field (EMF) in the MCG which considers the reduction response of each EMF reduction technology of the MCG including the MSR by referring to the signal measured by the reference magnetic sensor outside the MSR. The effect of the correction was evaluated for each channel of the MCG by using the EMF signal from the DC electrified railway as the magnetic noise source. The average value of the correction effect was 18.1 dB, the standard deviation (SD) was 4.1 dB, and the 2SD range was from 9.8 dB to 26.4 dB. From these results, it is suggested that the developed method has the possibility to improve the EMF in the MCG by more than 9 dB.

This paper reports AC breakdown properties of the mineral oil / the vegetable-oil-based insulating fluid containing water and the movement of water-drops under AC electric field in those oils. These results were showed as the following: (i) AC electric strength (Fb) of the mineral oil decreased sharply over several tens ppm of water. Fb of the vegetable-oil-based insulating fluid also decreased with the increase of water amount, but the low degree of inclination that compared with that of the mineral oil was showed. (ii) The water-drops movement in the mineral oil was active, but that in the vegetable-oil-based insulating fluid displayed the gentle movement in contrast.

According to IEC 62631- 3-2, surface resistivity is defined not only by materials itself but also by the electrode arrangement. We have examined the surface resistance of conductive and antistatic materials using the set of annular electrodes. It was clarified that the guard electrode has adversely affected to the measurements of the surface resistance in case that the material has certain conductivity and the thickness of specimen is less than the gap between the annular electrodes. In order to improve an accuracy of the surface resistance measurements, this paper proposes a quadra-electrode arrangement which has a couple of the annular electrodes set.

It is crucial to detect void and delamination which might exist in cast resin transformer, because these defects can reduce insulation performance of cast resin equipment. It is considered that detecting partial discharge (PD) is effective to diagnose equipment of power equipment. This paper presents novel PD location using X-ray irradiation and UHF method in actual 6.6 kV class cast resin transformer VT as well as sample simulating the defect. By scanning a copper plate installed in front of a X ray generator to limit the X-ray irradiation range, the defect position was successfully determined with 10 mm accuracy. it was also shown that PD source in a larger size 33 kV class VT can be located by the time of flight of the electromagnetic wave detection signal by UHF method.

An analysis between the atmospheric state change and lightning discharges in the autumn (from Sep to Nov. 2011 and 2016) seasons in Japan is presented in this paper. In evaluating the number of lightning activities, we calculated SSI which is used to predict thunderstorms. We confirmed that the modified SSI for the winter season can be effective for evaluating the lighting activities in the autumn season, meaning that the lighting discharges in this season tend to be affected by the low-level atmospheric state condition.