Magnetoresistance of a Wheatstone bridge with micron size Co zigzag wires

We have studied the room temperature magnetoresistance of Co zigzag wires w ith micrometer width by arranging the wires according to a Wheatstone bridg e configuration. Measurements of the magnetoresistance for different orient ations of the applied magnetic field reveal a different behavior. The first orientation, corresponding to a different angle between the magnetic field and the two pairs of wires forming the bridge, drives the bridge out of eq uilibrium. For this first orientation the measured magnetoresistance can be explained in terms of the classical theory for anisotropic magnetoresistan ce in ferromagnetic materials. For the second orientation, corresponding to an identical angle between the field and all four branches, the bridge is close to being in equilibrium. This provides an extra sensitivity, enabling to observe mesoscopic magnetic effects related to the motion, creation and annihilation of domain walls. Details about the domain structure have been obtained by magnetic force microscopy in the presence of a magnetic field. (C) 2001 Elsevier Science Ltd. All rights reserved.