Phase separation and perpendicular anisotropy of sputtered Fe-Cr films

Crystallographic structure and magnetic properties have been investigated in sputter-deposited Fe-Cr films in the wide composition range. The magnetic properties depend not only on the Cr concentration but also on the film structure which varies with input RF power and with film thickness. Perpendicular magnetization is observed in the films around 50 at% Cr in which the Fe-rich α-phase is precipitated in the σ-phase. The initial layer of the film with 40 - 60 at% Cr is in the χ-phase. The saturation magnetization of the film with perpendicular anisotropy is much smaller than that of bulk alloy due to the phase separation. The perpendicular magnetic anisotropy originates from the shape anisotropy of the precipitated α-phase with high Curie temperature. The phase separation is enhanced by applying magnetic field during sputtering.