Cr/SmCo/Cu/Cr thin films with high coercivity deposited at low pressure

•Apply the simple route to synthesis SmCo thin films with different compositions.•Adjusting the deposition pressure is effective to obtain the single phase thin film.•The coercivity of SmCo5 film is extremely high as 38 kOe at the low thickness.•Composition analysis by first-order-reversal curve and high temperature hysteresis loop.

The Cr/SmCo/Cu/Cr multi-layer thin films with high coercivity were prepared under low deposition pressure by using the magnetron sputtering. The as-deposited SmCo films show the amorphous structure while Sm2Co17 or SmCo5 hard magnetic phases appear upon annealing in vacuum furnace at temperature between 500 and 600 °C. It is also found that the SmCo phase transformation takes place from SmCo5 to Sm2Co17 with elevating deposition pressure from 2 to 5 m Torr. The post-annealing temperature has a great effect on the phase transition and the decomposition of the SmCo phase. It is found that the magnetic properties of the films including coercivity are dependent both on the deposition pressure and the annealing temperature. In-plane coercivity value of as high as 38 kOe was obtained for the SmCo film deposited at 2 m Torr pressure when annealed at 550 °C, while the coercivity drops down to 15 kOe when the annealing temperature of 600 °C was used because of the decomposition of SmCo phase. The results suggest that single phase SmCo thin films with high coercivity can be effectively produced by simply adjusting the synthesis parameters in magnetron sputtering system.