Orientational dependence of the exchange biasing in Ni-Fe/Mn_1-xNi_x(x=0.11,0.18,0.23) bilayers

The correlation between the exchange anisotropy of ferromagnetic (F)/antiferromagnetic (AF) bilayers and the spin alignment of antiferromagnet at the interface is still under question. In the present study, Mn_1-xNi_x (x=0.11,0.18,0.23) alloys, whose spin structure changes with x, were used for Ni-Fe/AF bilayers. The correlation between AF spin alignment at the interface and exchange anisotropy was investigated by controlling the preferred orientation of the bilayers. The crystal orientation of bilayers was changed by adding nitrogen into the sputtering argon gas only during the deposition of the Ni-Fe layer adjacent to the substrate. The preferred orientation was (111) when the nitrogen partial pressure, P_N2=0%-1%; (100) when P_N2>1%. When P_N2<1%, J_k decreased and H_c increased with increasing P_N2, because of the decrease of the grain size of γ-Mn-Ni. When P_N2 exceeds 1%, J_k increased discontinuously, accompanied by the orientational change of the bilayers.