Resistivity due to Domain Wall Excitation in Thin Wires
of Ferromagnetic Metals

Abstract

We study the influence of thermal excitation of a domain wall (DW) on resistivity in thin wires of disordered ferromagnetic metals. The negative correction for local conductivity δσ due to the DW excitation is calculated by assuming that the elastic mean free time of spin-up electrons τ₊ differs from that of spin-down electrons τ_-. When k_BT >> hω₀ (ω₀: attempt frequency of the DW), we obtain the correction arising inside the DW region as δσ/σ₀ = -cT/E_pin, where c ≈(τ₊ - τ_-)²/(6 τ₊ τ_-), σ₀ and E_pin denote Drude conductivity and the pinning energy for the DW, respectively. A magnetic field H parallel to the wire reduces E_pin and thereby enhances the negative correction. When H is close to the coercive field H_c, we find that δσ(H)/σ₀ ∝ -(1-H/H_c)^-1/2 as long as the DW is trapped at the pinning site.