Anisotropic magnetoresistance in facing-target reactively sputtered epitaxial γ′-Fe4N films

negative anisotropic magnetoresistance that comes from the spin-down conduction electrons are observed in facing-target sputtered epitaxial gamma'-Fe4N films with different film thicknesses, substrates and orientations. Anisotropic magnetoresistance of gamma'-Fe4N films on LaAlO3(1 0 0) is larger than other substrates. The magnitude of anisotropic magnetoresistance in (1 0 0)-oriented films is always larger than (11 0)-oriented films. The anisotropic magnetoresistance is intimately related to the magnetocrystalline anisotropy. Fourier coefficient C-2 theta and C-4 theta of cos 2 theta and cos 4 theta terms strongly depend on the measuring temperature. No significant influence of magnetic field on C-2 theta and C-4 theta appears. The marked change of C-2 theta and appearance of C-4 theta at low temperatures are from crystal field splitting of d orbitals induced by the lattice change due to the tensile stress from substrate and the compressive stress from decreased temperatures. (C) 2015 Elsevier Ltd. All rights reserved.