COERCIVITY AND MAGNETIC ANISOTROPY OF SINTERED SM2CO17-TYPE PERMANENT MAGNETS

Anisotropic and isotropic Sm2Co17-type permanent magnets have been prepared by using the conventional sintering technique. Transmission electron microscopy was used to characterize the cellular structure within the Sm2(Fe,Co)17 grains. Hysteresis loops (M∼H) were measured in the temperature range from 4.2 to about 1000 K by using a pulsed-field magnetometer with a maximum field strength up to 24 MA/m. The magnetocrystalline anisotropy field HA has been measured up to 1000 K by using the singular point detection technique on anisotropic samples with external fields applied perpendicular to the magnetic alignment direction. The saturation magnetization Ms has been measured on anisotropic samples with external fields applied parallel to the magnetic alignment direction. From studies of the coercivity mechanism by using a micromagnetic analysis of the temperature dependence of the coercivity field, it follows that the coercivity of Sm(Co,Fe,Cu,Zr)z is controlled at elevated temperature (above 520 K) by a nucl...