Reversible and irreversible magnetoresistance of quasisingle domain permalloy microstructures

Permalloy microstructures are investigated by magnetoresistance measurements at 2.0 K and by magnetic-force microscopy at room temperature. While the reversible anisotropic magnetoresistance is determined to be 2.4% at saturation fields of B-sat=1020 mT, the irreversible switching yields a resistance change of the order of 0.05% at 13 mT. By tilting the external magnetic field relative to the easy axis of the quasi single-domain microstructures insight in the reversal process is gained. Comparison with an analytical model provides evidence for magnetization reversal by curling. (C) 2004 American Institute of Physics.