Effect of Si/Fe Composition, Substrate Temperature, and Substrate Orientation on the Structure and Magnetic Properties of Fe-Si Alloy Film

Fe100–xSix (x = 0, 2, 6, 10 at. %) alloy films are prepared on MgO single-crystal substrates of (001), (110), and (111) orientations at temperatures ranging between room temperature and 600 °C by using a radio-frequency magnetron sputtering system. The film growth behavior, the crystallographic properties, and the magnetic properties are systematically investigated. Fe-Si(001) single-crystal films with bcc structure are formed on MgO(001) substrates. The Fe-Si films deposited on MgO(110) substrates consist of epitaxial bcc(211) bi-crystals whose orientations are rotated around the film normal by 180° each other. Fe-Si films grow epitaxially on MgO(111) substrates with two types of bcc(110) variant whose crystallographic orientations are similar to the Nishiyama-Wasserman and the Kurdjumov-Sachs relationships. The orientation dispersion of Fe-Si film decreases with decreasing the Si composition, with increasing the substrate temperature, and with decreasing the index of the substrate crystallographic plane. The Fe-Si films deposited on MgO(001) and (110) show in-plane magnetic anisotropies reflecting the magnetocrystalline anisotropies of bulk Fe-Si alloy crystals. The Fe-Si films deposited on MgO(111) show nearly isotropic in-plane magnetic anisotropies that possibly come from the multiple variant structure. The coercivity decreases with increasing the Si composition and with decreasing the substrate temperature.