Anisotropic and isotropicSm2Co17-type permanent magnets have been prepared by using the conventional sintering technique. Transmission electron microscopy was used to characterize the cellular structure within theSm2(Fe,Co)17grains. 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 fieldHAhas 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 magnetizationMshas 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 ofSm(Co,Fe,Cu,Zr)zis controlled at elevated temperature (above 520 K) by a nucleation process of reversal domains. ©1997 American Institute of Physics.