Magnetic and magneto-transport behavior in variable width Ni80Fe20 flat wires

In this letter, we present the results of a comprehensive study of the magnetic and magneto-transport properties in variable width wire arrays based on Ni80Fe20 films of thickness :30-50 nm. For fixed width structures, we observe a linear dependence of the coercivity H-c on the ratio t/w of thickness (t) to the width (w) for t/w less than or equal to 0.12. This result indicates that dipolar fields within each wire control the coercivity for small t/w. We have demonstrated that by carefully selecting different wire widths w(1) = 5 mu m and w(2) = 0.5 mu m (corresponding to different values of H-c) in adjacent wires and then alternating them in an array, the coercivity can be 'engineered'. Measurements were also carried out as a function of the inter-wire spacing s in order to study the effects of magnetostatic interactions. Marked changes in the switching held were observed as the inter-wire spacing is varied. Magneto-optic Kerr effect (MOKE) measurements were made as a function of the orientation of the applied field relative to the axis of the wire, in order to investigate the magnetization reversal process in this new geometry. We found two distinct switching mechanisms corresponding to the two wire widths. (C) 1998 Elsevier Science B.V. All rights reserved.