Resistivity and spontaneous anisotropy of resistivity in amorphous Fe_xSi_1-x films

Abstract

Amorphous Fe_xSi_1-x films have been obtained by triode sputtering. The samples are ferromagnetic, with T _x (the crystallization temperature) and T _c (the Curie temperature) both above 77 K within the composition range 0˙5 ≤ x ≤ 0˙77. The resistivity, ρ, and the spontaneous anisotropy of resistivity, (δρ/ρ) = (ρ|| - ρ|)/⊥, have been measured between 77 and 800 K (ρ|| and ρ⊥ are the resistivities with the saturation magnetization, M_s, parallel and perpendicular to the current direction, respectively). The behaviour of the resistivity shows strong evidence for a very short mean free path, and the temperature coefficient of the resistivity, α = (l/ρ)(dρ/dT), follows the Mooij correlation. A short mean free path, may preclude magnetic scattering effects in the isotropic resistivity. The spontaneous anisotropy of resistivity, however, shows an anisotropic contribution from magnetic scattering, having a clear dependence on M_s ², independent of composition and temperature. This behaviour deviates from linearity at both extremes of the composition range referred to above. For x ≤ 0˙55, magnetization fluctuations could explain the nonlinearity, while for x ≥ 0˙77, the microcrystallinity of the alloys is likely to be responsible.