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

• The negative and twofold symmetric AMR appears in epitaxial γ′-Fe4N films.
• The negative AMR can be attributed to the spin-down conduction electron.
• With the increased temperature, the absolute value of AMR (|AMR||AMR|) decreases.
• |AMR||AMR| of the (1 0 0)-oriented films is always larger than the (1 1 0)-oriented films.

The negative anisotropic magnetoresistance that comes from the spin-down conduction electrons are observed in facing-target sputtered epitaxial γ′-Fe4N films with different film thicknesses, substrates and orientations. Anisotropic magnetoresistance of γ′-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 (1 1 0)-oriented films. The anisotropic magnetoresistance is intimately related to the magnetocrystalline anisotropy. Fourier coefficient C2θ and C4θ of cos 2θ and cos 4θ terms strongly depend on the measuring temperature. No significant influence of magnetic field on C2θ and C4θ appears. The marked change of C2θ and appearance of C4θ 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.A. Magnetic materials; A. Nitrides; B. Epitaxial growth; D. Electrical properties

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