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