Abnormal temperature dependence of intrinsic coercivity in Sm(Co, Fe, Cu, Zr)z powder materials

The intrinsic coercivity H-ci in Sm(CobalCuxFe0.1Zr0.033)(z) powder materials was found to increase with increasing temperature when Cu content x = 0.048, but to decrease when Cu content x greater than or equal to 0.068. This abnormal behavior, which is also reversible, was found in a series of samples with various ratios z. The field dependence of the intrinsic coercivity suggests that the bonded magnets were fully saturated with an applied field of 20 kOe. The exposure to higher temperatures did not change the room temperature value of coercivity. This indicates that the microstructure does not change during the measurement from 573 to 773 K. The change of coercivity mechanism was found to be responsible for this abnormal temperature behavior. Monte Carlo simulation showed that the coercivity increases (decreases) with increasing temperature for the repulsive (attractive) cell boundary, which is consistent with the experimental results. (C) 1998 American Institute of Physics. [S0003-6951(98)03746-2].