Magnetoresistance magnetometry of (Ni80Fe20)1−xIrx wires with varying anisotropic magnetoresistance ratio

Abstract

We report room and low temperature magnetoresistance measurements on submicrometer scale elements (wires and crosses, 1.0, 0.5, and 0.1 μm) of (Ni80Fe20)1−xIrx (x≈2%) with varying Ir concentrations. For the particular Ir concentrations studied, the anisotropic magnetoresistance (AMR) ratio varied between −0.043% and −0.035% at room temperature. For the single wires (0.5–1 μm) the MR versus field characteristic is similar to that reported for Ni80Fe20 wires of similar size, but an opposite sign of the AMR is observed for x>2%. For H parallel to the wire axis, the reversal is determined by the sweeping of a few domains which give rise to “ears” in the MR–H characteristic. For H perpendicular to the wire, a parabolic variation is seen corresponding to rotation of the magnetization, but a negative slope in the MR-H characteristic is obtained at high fields as in permalloy wires. This suggests that the high field behavior originates from a distinctly different mechanism (e.g., surface scattering) from that of AMR.