Exchange bias in NiFe/granular-FeMn–MgO bilayers

Abstract

A series of polycrystalline NiFe/(FeMn)1−x(MgO)x bilayers with granular antiferromagnetic layers were prepared by magnetron sputtering. For a specific antiferromagnetic layer thickness, the intensity of the fcc (111) x-ray diffraction peaks from Cu, NiFe, and FeMn layers, and the FeMn grain size exhibit maxima at x=0.025. At this composition, significant enhancement in exchange field is observed together with slight change in coercivity. Remarkably, the training effect in exchange bias is greatly suppressed. These observations indicate the possibility of utilizing granular antiferromagnetic layers in magnetoelectronic devices to improve thermal stability.