Abnormal temperature dependence of intrinsic coercivity in sintered Sm-Co-based permanent magnets

In search of high-temperature permanent magnet materials, sintered Sm-Co-ba sed magnets with abnormal temperature dependence of intrinsic coercivity ha ve been obtained. These magnets have small negative, or near-zero, or large positive temperature coefficients of intrinsic coercivity. A model of coer civity mechanism has been proposed to explain this abnormal temperature dep endence. According to this model, the coercivity in 2:17-type permanent mag nets is controlled by two conflicting mechanisms. The first mechanism is th ermal activation, which leads to decreased coercivity with increasing tempe rature. The second mechanism can be explained by a pinning process in which increasing temperature may result in an increased difference of crystallin e anisotropy between the 2:17 cell phase and 1:5 cell boundary phase and, i n turn, a higher coercivity at high temperature. (C) 2000 American Institut e of Physics. [S0021-8979(00)77308-7].