Exchange anisotropy in PtMn/Ni/sub 80/Fe/sub 20/(110) quad-crystal films

Exchange anisotropy for an ordered tetragonal PtMn/Ni/sub 80/Fe/sub 20/(110) quad-crystal film grown on an Mo(001) step surface was studied. The PtMn/Ni/sub 80/Fe/sub 20/ bilayers grown at 300(degree)C show a unidirectional exchange anisotropy with the easy axis parallel to the underlying Mo stepedge direction. The azimuthal distribution of the coercive fields displays a fourfold symmetry. The azimuthal distribution of the coercive fields can be explained by the fourfold crystalline-induced interfacial strain between Ni/sub 80/Fe/sub 20/ and Mo. The azimuthal distribution of the exchange fields was mainly attributed to the step-induced unidirectional anisotropy and the biquadratic coupling between antiferromagnetic-ferromagnetic interface.