Size dependence of the magnetoresistance in submicron FeNi wires

The field-dependent magnetoresistance (MR) characteristic and magnetic hysteresis behavior has been studied in 300-500 Angstrom thickness Ni80Fe20 wires of variable width (w) in the range from 0.2 to 10 mu m. As the width of the wire decreases, a marked increase in the easy axis coercive field is seen for fields applied along the wire axis and the form of the MR characteristic is markedly modified for the in-plane perpendicular hard axis direction with a large field-dependent MR response observed for applied field strengths exceeding the edge demagnetizing field. The low field hard axis results are discussed in terms of-an inhomogeneous spin configuration across the width of the wires arising from the spatial variation of the demagnetizing field. (C) 1996 American Institute of Physics.