The history of MRAM development, including the toggling method and future perspectives were reviewed. Also, the giant TMR effect reported quite recently for MgO barrier junction and Heusler electrode junction was introduced In addition, spin dynamics, which are closely related with high speed and large capacity MRAM technologies, was shown. Especially, the enhancement of Gilbert damping constant was introduced.

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We have developed a three-dimensional (3-D) second-order gradiometer connected to 39-channel SQUIDs for vector measurement of magnetoencephalogram (MEG) that can simultaneously detect magnetic field components perpendicular and tangential to the scalp. Each coil is orthogonally wound with Nb-Ti wire on a rectangular solid of 3×3×6 cm. To assess discrimination and separation of multiple sources, we carried out both simulation study and 3-D vector measurement of MEG with mixed auditory evoked field (AEF) and somatosensory evoked field (SEF) overlapping in time. The magnetic field distribution perpendicular to the scalp was not helpful for estimating the location and number of sources, owing to the lack of a dipole pattern, but the magnetic field distribution tangential to the scalp can provide information about new constraint conditions by visual inspection. We estimated multiple sources of mixed AEF and SEF from the MEG data of the magnetic field tangential to the scalp, and confirmed the results by comparison with superimposed source locations in MRI of a subject's head.

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The effect of the thicknesses of Pd and Si films in the Pd/Si dual intermediate layer on magnetic properties of the Co/Pd multilayer for double-layered perpendicular magnetic recording medium was studied with the aim of developing an ultra-thin intermediate layer for producing fine magnetic clusters in the Co/Pd multilayered film. The magnetic properties were found to be strongly dependent on the ratio of the Pd or Si layer thickness to the total thickness of the Pd/Si dual film. When the ratio of the Pd layer thickness to the total thickness was 0.7-0.8, high perpendicular coercivity and small slope parameter of the major hysteresis loop were attained simultaneously, which resulted from weak intergranular exchange coupling of the Co/Pd multilayered film. In addition, the total thickness of the Pd/Si intermediate layer was successfully reduced to 4 nm, while retaining its high perpendicular coercivity and fine magnetic clusters, by optimizing the thicknesses of Pd and Si layers. Read-write experiments revealed that improvements in reproducing resolution and signal-to-noise ratio of the Co/Pd multilayered media were achieved by the decrease in the intermediate layer thickness.

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Nanoparticulate FePt, which is highly stable under heating, is a very promising magnetic material for future super-highdensity magnetic recording media. The FePt and FePtCu nanoparticles were synthesized by a reverse micelle method (H₂O/sodium bis (2-ethylhexyl) sulfosuccinate (AOT)/decane). FePt and FePtCu nanoparticles obtained with this method exhibited monodispersity and homogeneous elemental composition (both coefficients of variation are less than 10%), and the average diameter of these particles was able to arbitrarily controlled between 3 and 9 nm. Further, annealing of the FePtCu nanoparticles in an Ar+H₂ (5%) gas lowered the temperature for modification from fcc to fct by way of the oxidation state to the range of 350°C-375°C. Nanoparticulate FePt and FePtCu media coated on glass substrates had a surface roughness (Ra) of less than 1 nm and showed magnetic recording capability.

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Ferromagnetic semiconductor EuO and Gd_xEu_1-xO (0.01<x<0.05) thin films were prepared by a reactive deposition method in an ultra-high-vacuum deposition system. Aluminum capping and a combination of Ar treatment and CaF₂ capping are effective for protecting sample films. Both oxygen-deficient and Gd-doped EuO films were examined as electron-doped ferromagnetic semiconductors. The Gd doping looks more promising due to the chemical stability and the better electron doping controllability.

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Exchange coupling between half-metallic Fe₃O₄ and antiferromagnetic PtMn, MnIr, and CrMnPt films was investigated, with the goal of inducing unidirectional anisotropy in the Fe₃O₄ film, which has hard magnetic properties. The Fe₃O₄-CrMnPt system exhibited superior exchange coupling properties: a large unidirectional anisotropy constant (K_e) of -0.15 -0.18 erg/cm², a high blocking temperature (T_B) of -320°C, and a nearly unidirectionally shifted M-H curve. In the Fe₃O₄-PtMn system, the K_e value degraded to around zero. The oxygen in the Fe₃O₄ film diffused into the adjacent films through thermal annealing to produce PtMn-phase transition, resulting in considerable K_e degradation. In the Fe₃O₄ -MnIr system, the K_e and T_B values were a little too low for practical application. From these results, it is reasonable to suppose that the most suitable antiferromagnetic material for pinning Fe₃O₄ film in spintronics devices is CrMnPt.

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