Tunable phase formation in Ni-Fe thin films at nanoscale using high magnetic fields

The effect of a high magnetic field on phase formation and determination in Ni-Fe film at nanoscale is reported. The bcc structure of the film changed to the coexistence of bcc and fcc phases by increasing the substrate temperature from 25 to 200 to 400 °C without magnetic field. Under a 6 T magnetic field, a coexistence of bcc and fcc phases was formed whatever structures the films prepared without magnetic field are. Furthermore, each nanograin exhibited only a single phase. The effect of high magnetic field indicates that the reduction in the Gibbs free energy (entropy) for the fcc phase by the high magnetic field is larger than that for the bcc phase. Furthermore, the reduction is different for various substrate temperatures. The results indicate that the phase formation is tunable at the nanoscale under high magnetic field.