Electric and magnetic evolution in sputter-deposited Fe_xSi_1-x alloy films

Fe_xSi_1-x alloy films have been prepared by an rf sputter-deposition method. X-ray diffraction patterns indicate that an amorphous phase is formed for x < 0.8. Temperature dependence of electrical resistivity indicates the following electric evolution. Carrier-excitation from the impurity to the conduction (or valence) bands is dominant for x < 0.2 (the semiconductor regime), the band conduction is affected by strong impurity- and random-scatterings for x > 0.4 (the metallic regime), and the carrier-excitation between the impurity band and the mobility edge is retained due to the electron-localization effect in the amorphous structure for 0.2 < x < 0.4 (the transition region). The thermomagnetic- and magnetization-curves indicate the following magnetic evolution. The ferromagnetic phase appears at x ≅ 0.3 and the Curie temperature rapidly increases with increasing x. The magnetic (spin- or cluster-) glass region is very narrow (x = 0.3 ∼ 0.55) at low temperature. These magnetic behaviors are ascribed to the instability of Fe magnetic moments and the depression of RKKY interactions in the low x range.