Spin-dependent electrical transport in ion-beam sputter deposited Fe-Cr multilayers

Abstract

The temperature dependence of the electrical resistivity and magnetoresistance of Xe-ion beam sputtered Fe-Cr multilayers has been investigated. The electrical resistivity between 5 and 300 K in the fully ferromagnetic state, obtained by applying a field beyond the saturation field (H_sat) necessary for the antiferromagnetic(AF)-ferromagnetic(FM) field-induced transition, shows evidence of spin-disorder resistivity as in crystalline Fe and an s-d scattering contribution (as in 3d metals and alloys). The sublattice magnetization m(T) in these multilayers has been calculated in terms of the planar and interlayer exchange energies. The additional spin-dependent scattering Δρ(T) = ρ(T,H=0)_AF - ρ(T,H=H_sat)_FM in the AF state over a wide range of temperature is found to be proportional to the sublattice magnetization, both Δρ(T) and m(T) reducing along with the antiferromagnetic fraction. At intermediate fields, the spin-dependent part of the electrical resistivity (ρ_s (T)) fits well to the power law ρ_s (T) = b - cT^αwhere c is a constant and b and αare functions of H. At low fields α\approx 2 and the intercept b decreases with H much the same way as the decrease of Δρ(T) with T. A phase diagram (T vs. H_sat) is obtained for the field- induced AF to FM transition. Comparisons are made between the present investigation and similar studies using dc magnetron sputtered and molecular beam epitaxy (MBE) grown Fe-Cr multilayers.