Development of industrial nanocomposite permanent magnets (NCPM) is reviewed with a particular emphasis on rare-earth-iron-based materials. After a brief description of the basic concepts concerning NCPM, leading discoveries of iron-based NCPM are reviewed. The impact of recent development of high-coercivity Nd-Fe-B-Ti-C isotropic NCPM powders that are industrially produced by applying strip casting process for rapid solidification is described. Short comments on bulk NCPM and empirical efforts toward anisotropic NCPM are also included. Application aspects of the industrial NCPM are discussed.

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Effects of the preparation condition on magnetic properties were investigated in isotropic TbCu₇-type Sm-Zr-Fe-Co-N materials made by the melt-spinning process. All the Sm-Zr-Fe-Co powders melt-spun with wheel speeds of 30-40 m/s showed a single-phase structure with crystalline TbCu₇. The grain size of the powder decreased monotonically with the increase of the wheel speed. The H_cJ, B_r and (BH) _max of the powder increased with decreasing grain size. In this study, maximum hard magnetic property was achieved in Sm _8.7 Zr _1.0 Fe _85.8 Co _4.5 N_x powder melt-spun at 40 m/s. A compression-molded bonded magnet using powder melt-spun with at a wheel speed of 40 m/s showed excellent hard magnetic properties: B_r=0.83 T, H_cJ=720.5 kA/m, (BH) _max=113.9 kJ/m ³. These results show that the TbCu₇-type Sm-Fe-N material has high performance and practicality for isotropic bonded magnets.

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We studied the magnetic anisotropy in an FeSiC soft magnetic film. The film was deposited at room temperature without applying a magnetic field using conventional DC magnetron sputtering. The as-deposited film had a fine-crystalline structure and a magnetic easy axis in the radial direction of the disk substrate without any textures. The radial magnetic anisotropy in the film was not induced by film stress because it was produced even when there was no film stress. The film was found not to have the anisotropic arrangement of the fine-crystal grains because the electron-beam diffraction pattern was a ring pattern. This meant that the radial magnetic anisotropy in the film was not the magnetocrystalline anisotropy. The anisotropy field was strongly dependent on the distance from the center of the disk substrate. Our findings suggested that the radial magnetic anisotropy in the fine-crystalline FeSiC soft magnetic film was caused by the nano-scale directional deposition of the sputtered particles.

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The magnetization behavior of antiferromagnetically coupled ferromagnetic bilayers with a uniaxial anisotropy is investigated analytically, with the aid of numeric calculation. Field trajectories giving a constant angle to the magnetization of one of the two layers, leaving the other as a variable in the in-plane field two-dimensional co-ordinate, and their envelopes are used to understand the magnetization behavior, including switching. These tools provide a good means of optimizing magnetic parameters to maximize the operating field margins of the recently proposed toggle-mode MRAM devices, including the thermal relaxation. Control of the especially low exchange coupling required for performance optimization is identified as a key technical issue, as well as increase of the operating field strength.

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