Crystal structure and magnetic properties of hard magnetic Sm2Fe17Nδ thin films with Co substitution

Abstract The crystal structure and magnetic properties of the hard magnetic Sm 2 (Fe 1− x Co x ) 17 N δ thin films prepared by dc magnetron sputtering and subsequent nitrogenation process were investigated. It is found that the N content and crystal structure determine the non-monotonic dependence of the coercivity H C on nitriding temperature for the films with x =0. With nitriding temperature exceeding 300 °C, N atoms can enter the Sm 2 Fe 17 phase and the N content increases with increasing nitriding temperature, which leads to an increased coercivity. However, the maximum value of the H C is observed at 400 °C. The α-Fe soft phase appears with nitriding temperature further increasing to 500 °C, which is responsible for the decreased H C . When x is between 0 and 0.36, the films exhibit single Th 2 Zn 17 -type structure. Co atoms are found to go into the lattice of the 2:17 phase, generating an enhanced exchange coupling interaction between the nano-grains, which is responsible for the improved hard magnetic properties of the films with Co substitution at a certain range. Especially, the optimal value of the coercivity H C and remanence ratio M R / M S reaches 4.0 kOe and 0.70 for the films with x =0.17 and 0.36, respectively.