Domain wall resistivity in epitaxial thin film microstructures

This article reviews our recent experimental studies of domain wall (DW) resistivity in epitaxial transition metal ferromagnetic thin film microstructures with stripe domains. The results are presented and analysed in the context of models of DW scattering and conventional magnetoresistance (MR) effects in ferromagnetic metals. Microstructures of progressively higher magnetic anisotropy and thus smaller DW widths have been studied, including; bcc Fe, hcp Co and L1_o FePt. The magnetic domain structure of these materials have been investigated using magnetic force microscopy and micromagnetic simulations. In Fe and Co the dominant sources of low-field MR are ferromagnetic resistivity anisotropy, due to both anisotropic MR (AMR) and the Lorentz MR. In Fe, at low temperature, a novel negative DW contribution to the MR has been found. Hcp Co microstructures show a greater resistivity for current perpendicular to DWs than for current parallel to DWs, that is consistent with a small (positive) DW resistivity and a Hall effect mechanism. High anisotropy L1_o FePt microstructures show strong evidence for an intrinsic DW contribution to the resistivity. Related studies and future directions are also discussed.