To apply Nd–Fe–B thin films for mass-produced heat-assisted magnetic recording media, we investigated the high-rate sputtering conditions required to obtain c-axis textured Nd2Fe14B thin films and analyzed the growth mechanism. Magnetization curves indicated that higher substrate temperatures and sputtering rates resulted in a higher degree of perpendicular magnetic anisotropy; a Nd–Fe–B layer deposited at a substrate temperature (Tsub_0) of 600 °C and a sputtering rate (Rsp) of 2.6 nm/s had the easy axis perpendicular to the film plane. The dependence of the magnetic properties on the sputtering rate was due to a decrease in the substrate temperature during sputtering; there was a threshold for obtaining a high squareness ratio. X-ray diffraction analysis and transmission electron microscopy (TEM) images showed that the c-axis textured Nd2Fe14B crystal phase was formed in the Nd–Fe–B layer deposited at Tsub_0 = 600 °C and Rsp = 2.6 nm/s, which resulted in the highly perpendicular magnetic anisotropy. In addition, the TEM images showed a layer of Nd2Fe14B with no obvious lattice fringes near the interface between the Nd–Fe–B layer and Mo underlayer, while the lattice fringes of the Nd2Fe14B phase were not parallel to this interface but gently curved along the Mo cap layer. We propose that the c-axis orientation was achieved by the rotation of the c plane, which has the lowest surface energy in the Nd2Fe14B phase, toward the vacuum-side surface during sputtering.

A decrease in the crystallite diameter of ferrites irradiated with microwaves has been considered as a non-thermal effect of so-called de-crystallization; however, its mechanism has not been elucidated. We hypothesized that a decrease in the crystallite diameter is caused by interaction between the ordered spins of ferrite and the magnetic field of microwaves. To verify this, we focused on magnetite with a Curie temperature of 585 °C. Temperature dependence around this temperature and time dependence of the crystallite diameter of the magnetite irradiated with microwaves at different temperatures and durations were investigated. From the X-ray diffraction data, the crystallite diameter of magnetite exhibited a minimum value at 500 °C, just below the Curie temperature of magnetite, where the energy loss of the interaction between magnetite’s spins and the microwaves takes the maximum value. The crystallite diameter exhibited a minimum value at 5 min irradiation time, during which the microwaves were excessively absorbed. Transmission electron microscopy observations showed that the microstructure of irradiated magnetite in this study was different from that reported previously, indicating that a decrease in the crystallite diameter is not caused by de-crystallization but its similar phenomenon. A decrease in coercivity and lowering temperature of Verwey transition were observed, evidencing decreased crystallite diameter. This study can thus contribute to the development of the theory of a non-thermal effect.

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The correlation between compression conditions at temperatures in the range of 573-773 K with strain rate range of 0.002Ϫ2 s Ϫ1 and grain size after solution heat treatment SHT of 6061 aluminum alloy, was investigated. It is concluded that the grain coarsening occurred under specific Zener-Hollomon parameters of 10 8 ϳ2ϫ10 12 s Ϫ1. This phenomenon could be explained by crystalline orientation analysis and stored deformation energy evaluation. Small Z parameter condition could get low stored strain with fine grains which were stable during SHT. High Z parameter condition could get high stored strain, so a lot of small recrystallized grains were formed after SHT. Effect of Cr and Zr contents on the grain size of 6061 aluminum alloy was also investigated. Grains were fine when 0.34 mass%Cr or 0.17 mass%Cr and 0.14 mass%Zr were added due to pinning effects of Cr bearing dispersoids and Zr bearing dispersoids to grainboundaries.

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