Weak magnetic moment on IrMn exchange bias pinning layers

We present evidence from soft x-ray resonant magnetic scattering measuremen ts at the Mn L-3 edge for the existence of a small magnetic moment on the a ntiferromagnetic IrMn pinning layer in a NiFe/Cu/Co/IrMn spin valve structu re. The variation of the signal in an applied magnetic field shows that the moment lies antiparallel to the Co moment. Changes in the Mn L-3 edge sign al as the Co moment is rotated into the hard direction are rapid and do not appear to be associated with thermal reordering of the antiferromagnetic d omain structure. (C) 2001 American Institute of Physics.