Improved thermal stability of exchange bias of Mn–Ir/Co–Fe bilayers by novel in situ thermal annealing procedure

Abstract

The effect of in situ thermal annealing of Mn–Ir films under ultra-high vacuum on the metallurgical microstructure and on the thermal stability of the unidirectional anisotropy constant, JK, was investigated for Mn73Ir27/Co70Fe30 bilayers. As a result, we found that the average lateral grain size of Mn–Ir increases with increasing the in situ annealing temperature, TIR and that the shape of JK–T curve changes to convex with increasing the TIR, implying a narrowing distribution of local blocking temperature. We conclude that ultra-high vacuum annealing is effective in improving the thermal stability of the exchange anisotropy of Mn–Ir/Co–Fe bilayers through the change of lateral grain size distribution of the Mn–Ir layer.