Magnetization reversal processes in exchange-biased systems

Abstract

The magnetization reversal mechanism in sputtered bilayer films of NiFe coupled to a range of antiferromagnets has been studied using Lorentz microscopy and magnetic measurements. The reversal mechanism on the forward and recoil loops appears different and the results have been interpreted in terms of a recently published seven-point model. Reversal is controlled by the magnetic domain structure in the antiferromagnet. Time-dependent studies show that the reversal field for the NiFe layer decreases for both the forward and recoil loops, as the time for which the film is held above the saturation field of the NiFe layer increases. This can be explained by viscous rotation of the magnetization in thermally activated domains in the antiferromagnetic layer.