Exchange bias measurements of CoFe/IrMn

The exchange bias anisotropy field in CoFe/IrMn ferromagnetic/antiferromagn etic bilayers has been investigated by two different experimental probes. O ne was the traditional hysteresis loop shift technique and the other was a recently developed technique which monitors small reversible rotations of t he magnetization with the anisotropic magnetoresistance (AMR). All the samp les show approximately twice the exchange bias anisotropy field measured wi th the AMR technique compared to that measured with the traditional hystere sis loop method. Based on similar experiments in other materials, there is a portion of the exchange bias uniaxial anisotropy which rotates in a hyste resis loop measurement. It is surmised it is this energy which the hysteres is loop technique neglects and that the AMR technique is a better measure o f the exchange bias anisotropy energy. (C) 2001 American Institute of Physi cs.