Evidence for a high-spin Fe state in fcc Fe1-xNix thin films in the invar region

Abstract Fe 1- x Ni x alloy films with compositions in the Invar region (0.32 x M ( B , T ) was measured for 0 T B 1- x Ni x electron Mossbauer spectra (CEMS) were taken at room temperature for each Fe 1- x Ni x film as-prepared and after annealing It is possible to achieve Fe 1- x Ni x films as-prepared with pure fcc-structure and also mixtures of bcc and fcc phases. As-prepared films show, in contrast to the behavior of bulk Fe - x Ni x samples, high magnetic saturation moments M s and and large mean hyperfine-fields B hf which follow the Slater-Pauling curve. After annealing the films exhibit bulk behavior. We conclude that Fe 1- x Ni x films as prepared are in a magnetic state of the fcc-phase which is probably related to the occurence of γ 2 -Fe. By annealing the films these states convert into the metastable γ-state of the fcc phase with corresponding changes of the magnetic moment and the mean hyperfine field B B hf .