Approach to optimize the pinning effect of a NiMn layer with reduced thickness under a much shortened annealing process

We investigated the magnetic properties of sputtered Ni0.8Fe0.2/Ni1-xMnx (0.43less than or equal to xless than or equal to0.70) bilayers and found that an antiferromagnetic equiatomic NiMn layer could be formed through Mn diffusion with reduced thickness and a much shortened annealing time if the Ni1-xMnx layer is off-stoichiometric with suitable excess Mn. An overdose of Mn in a NiMn precursor layer was demonstrated to enhance the migration and the diffusion of Mn atoms, which seemed to promote the formation of antiferromagnetic NiMn of the theta phase, but in the mean time led to the deterioration of the adjacent ferromagnetic layer. We thus introduced the nano-oxide layer in the ferromagnetic layer near the interface of ferromagnetic and antiferromagnetic layers, which was proven to be very efficient to prevent Mn atoms from further intruding into the ferromagnetic layer even in the case that a large amount of Mn atoms were involved. As a result, a ferromagnetic layer pinned by a NiMn layer with excellent performance has been developed in a much simplified process. (C) 2003 American Institute of Physics.