Large exchange bias in interdiffused NiFe/Mn bilayers

The effect of the annealing temperature a well as the antiferromagnetic (AF) and ferromagnetic (F) thickness on exchange coupling in Ni81Fe19/Mn single bilayers was systematically studied. We then show that a large exchange coupling is observed when the bilayers are annealed at 300 degreesC: it corresponds to an exchange field of about 290 Oe. This large exchange field is induced with a rather thick F layer of 46 nm. Both the exchange field H-ex and coercive field H-c increase with Mn thickness reaching saturation around 100 nm of Mn. The exchange coupling is associated with interfacial diffusion at the NiFe/Mn interface. This result is confirmed by a large change in magnetization and resistivity before and after annealing. We show that the existence of the exchange field is associated with the clear evidence of a new FeMnNi phase in the x-ray spectrum. (C) 2002 American Institute of Physics.