Temperature dependence of coercivity and magnetization reversal mechanism in Sm(CobalFe0.1CuyZr0.04) 7.0 magnets

The temperature dependence of coercivity in Sm(Co_balFe _0.1Cu_yZr_0.04)_7.0 magnets with y=0 to 0.20 has been systematically studied. Two models are discussed with respect to the temperature dependence of coercivity. One model considers only domain wall (DW) pinning and explains the “abnormal” behavior as a temperature-induced transition from a repulsive DW pinning to an attractive one. The other model assumes a combination of pinning and nucleation of DWs in magnetically isolated 2:17 cells. In this model, the cell-boundary pinning of DWs takes place in the alloys with low Cu content at temperatures below the Curie temperature of 1:5 phase. Nucleation controls the magnetization reversal in the case of complete magnetic isolation of the 2:17 cells. This condition is expected to be fulfilled at any temperature above RT in the Cu-rich magnets, and only above Curie temperature of the 1:5 phase in the alloys with lower Cu content