Magneto-optical (MO) imaging using an MO material is one of the most important imaging techniques for measuring magnetic field distributions. The technique is attracting attention because of its ability to visualize magnetic fields and current distributions at a wide range of temperatures from cryogenic to room temperature or higher, a wide range of length scales from micrometers to several tens of centimeters, and a wide range of frequencies from DC to GHz. Nevertheless, further development of films with good MO properties is required in order to extend the range of applications of MO imaging. In this paper, developments related to bismuth-substituted iron garnet films, R_3−xBi_xFe_5−yGa_yO₁₂ (R = Y, Nd; 1 ≤ x ≤ 3), prepared by metal–organic decomposition for MO imaging plates are reviewed. In addition, an MO imaging plate with an electroluminescent backlight, which enables wide-area MO imaging, and the MO color imaging technique, which indicates the strength of a magnetic field using colors, are reviewed.

  (001)-oriented MnGa films were grown on thermally oxidized Si substrates using CoGa buffer layers by the magnetron sputtering method. The deposition and annealing temperatures of the CoGa buffer layer were optimized to improve (001)-orientation of the MnGa layer. As a result, a saturation magnetization of 290 emu/cc was obtained when CoGa was sputter-deposited at 400 ˚C and post-annealed at 700 ˚C. This saturation magnetization was almost equal to that of MnGa grown on an MgO(001) substrate. The (001)-oriented MnGa film grown on the Si substrate had surface roughness compared to that grown on MgO(001) due to the high temperature annealing of the CoGa layer. Improvement of surface flatness is necessary for applications to magnetic memory and storage such as magnetic tunnel junctions and bit patterned media.

  We design media for three-dimensional heat-assisted magnetic recording at 2 Tbpsi (total density of 4 Tbpsi), taking account of heat transfer simulation, field calculation, and information stability in high Curie temperature (HC) and low Curie temperature (LC) layers. The medium surface temperature while writing in the HC layer, the thermal gradients while writing in the HC and LC layers, and the grain temperature difference between the HC and LC layers while writing in the LC layer are discussed by using a heat transfer simulation. The magnetic field strength as a function of distance from the layer surface for a single layer is discussed by employing a field calculation. The Curie temperatures of T_LC and T_HC, and the grain heights of h_LC and h_HC in the LC and HC layers, respectively, are also discussed in terms of information stability during 10 years of archiving and writing in the LC layer. As a result, a media structure is decided whereby the upper, namely, the surface layer is an LC layer with T_LC = 625 K and h_LC = 4.5 nm, and the lower layer is an HC layer with T_HC = 750 K and h_HC = 6.0 nm with an anisotropy constant ratio of 0.8.