Zhang Dongtao

Structure and Magnetic Properties of Sm2Fe17Nx Sintering Magnets Prepared by Spark Plasma Sintering

Abstract Bulk Sm2Fe17Nx sintering magnet was fabricated by spark plasma sintering(SPS) technique. The effects of sintering pressure and sintering temperature on the magnetic properties of the Sm2Fe17Nx magnet were investigated. As a result, the density of the magnet is obviously improved with the increase of sintering pressure, but the coercivity drops since Sm2Fe17Nx has decomposed into SmN, α-Fe and N2. When sintering temperature was only above 200 °C under 1 GPa sintering pressure, the coercivity even begins to decrease, which indicates that high pressure promotes the decomposition of the Sm2Fe17Nx at lower temperature. The decomposition is also proved by the decrease of nitrogen and increase of α-Fe in the magnets.

Influence of Tm on Crystal Structure and Magnetic Properties of SmCo5 Compounds

Abstract The compounds of SmCo5 and Sm0.8Tm0.2Co5.2 have been studied via X-ray diffraction (XRD) and magnetic measurements, in order to clarify the effect of Tm doping on the crystal structure and intrinsic magnetic properties of the SmCo5 compound. XRD results show that both compounds have a single hexagonal CaCu5 type crystal structure, and the Tm doping leads to an expansion of the hexagonal unit cell in the direction of c axis and a contraction of a, b axes and the cell volume. The Curie temperatures (TC) of the SmCo5 and Sm0.8Tm0.2Co5.2 are 957 and 965 K, respectively. Magnetic measurements show that both the magnetic anisotropy field (HA) and the magnetization at an applied field of 7 T (M7T) of SmCo5 are higher than those of Sm0.8Tm0.2Co5.2 at room temperature (300 K). However, the HA and M7T of SmCo5 become lower than those of Sm0.8Tm0.2Co5.2 with the temperature increasing to 473 K. Therefore, it is concluded that Tm doping in SmCo5 can effectively improve the magnetic properties at elevated temperature.