Exchange coupling field and blocking temperature of Mn-Ir/Ni-Fe top/bottom bilayers with different stacking sequences and buffer layers

The exchange coupling field (H_ex) and the blocking temperature (T_b) were investigated with different stacking sequences and buffer layer materials. The top structure exhibited higher H_ex and T_b values than the bottom structure did. The samples which had high H_ex values also exhibited high T_b values. The curve shape of the temperature dependence of H_ex/H_ex(initial) changed from a concave type to a convex type with an increase in H_ex and T_b values. The H_ex and the T_b values may be related to grain size and to the distribution of antiferromagnetic grain size at the interface of the antiferromagnetic and the ferromagnetic layers. On the contrary, the values of coercivity field (H_c) may be related to the interface morphology and to the grain size distribution.