Anomalous Anisotropic Magnetoresistance in Pseudo-Single-Crystal gamma '-Fe4N Films

The negative anisotropic magnetoresistance (AMR) effect is observed in pseudo-single-crystal gamma'-Fe4N films from 4 to 300 K. Below 50 K, the changes in the AMR ratio depend on the crystal direction along which the sensing current flows. A large stepwise change of the AMR ratio is observed along the [100] direction. The anomalous cos(4 theta) component appears on the AMR curves below 30 K. A first-principles calculation of gamma'-Fe4N indicates that the electron occupation of the 3d orbitals is modified as the magnetic moment direction changes with respect to the crystal axes. The anomalous behavior of the AMR effect might be due to the change of the partial density of states of 3d-orbitals at the Fermi level. (C) 2010 The Japan Society of Applied Physics