Domain wall resistivity in epitaxial thin film microstructures

This article reviews our recent experimental studies of domain wall (DW) re sistivity in epitaxial transition metal ferromagnetic thin film microstruct ures with stripe domains. The results are presented and analysed in the con text of models of DW scattering and conventional magnetoresistance (MR) eff ects in ferromagnetic metals. Microstructures of progressively higher magne tic anisotropy and thus smaller DW widths have been studied, including; bcc Fe, hcp Co and L1(o) FePt. The magnetic domain structure of these material s have been investigated using magnetic force microscopy and micromagnetic simulations. In Fe and Co the dominant sources of low-field MR are ferromag netic resistivity anisotropy, due to both anisotropic MR (AMR) and the Lore ntz 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 cu rrent perpendicular to DWs than for current parallel to DWs, that is consis tent with a small (positive) DW resistivity and a Hall effect mechanism. Hi gh anisotropy L1(o) FePt microstructures show strong evidence for an intrin sic DW contribution to the resistivity. Related studies and future directio ns are also discussed.