Phase transformation and magnetic hardening in electrodeposited, equiatomic Fe–Pt films

Fe–Pt films were electrodeposited from an alkaline electrolyte containing Fe as a citrate complex and Pt as an amino-nitrite. Up to 6 at.% oxygen was present in as-deposited films, much lower than the 30 at.% value reported for Fe–Pt films deposited from weakly complexing, acidic electrolytes. Pt-rich films exhibit a face-centered cubic structure; nearly equiatomic films are transformed to the stable tetragonal structure by thermal annealing between 400 and 700 °C in forming gas. In films with thickness ranging from 13 to 93 nm, phase transformation occurs at lower temperatures in thicker films. 93 nm thick films exhibit a coercivity of 13 kOe after annealing at 450 °C, a temperature much lower than that required to achieve full magnetic hardening when growing from weakly complexing, acidic solutions.