Crystal Structure and Magnetic Properties of Sm₂Fe₁₇N_δ Thin Films Deposited on Si (100) Substrates

This work focuses on the crystal structure and magnetic properties of the hard magnetic Sm₂Fe₁₇N_δ films prepared by dc magnetron sputtering and the subsequent nitriding process. The XRD, EDS, M-H and M-T data show that N enters the cell structure and the films with the single Th₂Zn₁₇ phase are obtained when the nitriding temperature varies from 300 to 400°C, thus the maximum value of the coercivity H_C reaches 2561.7Oe. However, the Sm₂Fe₁₇ phase decomposes to the SmN nonmagnetic phase and the α-Fe soft magnetic phase with further increasing nitriding temperature, which corresponds to the decreasing H_C. Furthermore, the easy magnetization direction (EMD) is found to locate randomly in the film plane. This texture can not give an excellent M_R/M_S higher than the Stoner-Wohlfarth limitation (M_R/M_S=0.5), which agrees well with the observed low M_R/M_S (0.58). It is suggested that the magnetization reversal process is dominated by the nucleation mechanism according to the initial magnetization curve and the dependence of H_C on the field H.