Nd-Fe-B/α-Fe系ナノコンポジット薄膜の磁気特性  [in Japanese] Magnetic Properties of Nd-Fe-B/α-Fe Nanocomposite Thin Films  [in Japanese]

Thin films consisting of randomly distributed Nd_2Fe_<14>B and α-Fe phases were fabricated on glass substrates by rfsputtering. Although the existence of both Nd_2Fe_<14>B and α-Fe phases were confirmed by X-ray diffraction, the magnetization curves showed a single-phase-like behavilr. This result indicates exchange coupling between the Nd_2Fe_<14>B and Fe phases. On the basis of Rietveld analysis of the X-ray diffraction profiles, the volume fractions of the Nd_2Fe_<14>B and Fe phases were estimated. With an increase in the volume fraction of Fe (V_<Fe>) from 5% to 76%, H_c decreased from 12.3 to 0.8 KOe, while M_r/M_s increased from 0.54 to 0.83. The mean grain size, which was estimated from the widths of the X-ray diffraction peaks, decreased with increasing V_<Fe>. Micromagnetic calculations of magnetization curves suggested that the effective exchange coupling between the soft and hard phases becomes larger with increasing V_<Fe>, because of the decreasing grain sizes.