Magnetic properties of Fe–Pt thick-film magnets prepared by RF sputtering

Thick films of L10 ordered Fe–Pt alloy magnet with a high maximum energy product were prepared by using a three-dimensional sputtering apparatus. With decreasing the Ar pressure from 3 to 0.6 Pa, the films annealed at 600 °C underwent a gradual phase transformation from the disordered FCC phase to the ordered FCT one. With further decreasing the pressure to 0.43 Pa, the disordered phase appeared again. The values of HcHc and (BH)max(BH)max were maximized to be approximately 399 kA/m and 90 kJ/m3 at 0.6 Pa of Ar pressure, respectively. While varying the input power at a stable pressure of 0.6 Pa, the as-deposited samples were dominated by the disordered phase at the applied power of 100 W RF, and the heat treatment resulted in a change to such L10 ordered phase. At input power higher than 120 W, both the as-deposited and annealing samples were ordered to the hard L10 FCT phase, and high HcHc and (BH)max(BH)max values of about 446 kA/m and 124 kJ/m3, respectively, were obtained on the sample deposited at the input power of 180 W.