Structural and magnetic features of the solid-state synthesis and martensitic transformations in Ni/Fe(001)/MgO(001) thin films

Abstract The results of the experimental study of phase transformations occurring in Ni/Fe(0 0 1)/MgO(0 0 1) thin films with 3Fe:1Ni atomic composition during annealing at temperatures up to 650 °C and cooling to liquid nitrogen temperature are presented. Comparative analysis of previous and current results suggests that the paramagnetic phase γ par present in the invar of Ni 1− x Fe x alloys is the γ-Fe 3 Ni phase with the lattice parameter a =0.3600 nm. Measurements of magnetization of the samples in dependence of composition allowed one to determine a single-phase region of γ par phase existence in thin films limited by 75 at% Fe. It is shown that the temperature of γ par phase initiation during the solid-state synthesis coincides with the temperature A S of the reverse martensitic α′→γ par transition ( A S = T 0 ∼550 °C).