Temperature dependence of the magnetization reversal in Sm(Co,Fe,Cu,Zr)zSm(Co,Fe,Cu,Zr)z magnets

The magnetization reversal for traditional cell-structured Sm(Co,Fe,Cu,Zr)zSm(Co,Fe,Cu,Zr)z magnets has been investigated using micromagnetic finite element method. The variation of coercivity mechanism with temperature is observed. With the increase of temperature, the transition of coercivity mechanism from domain-wall pinning to reversed-domain nucleation happens at about 700 K. At the temperature below 700 K, the nucleation of reversed domain in the cell wall with weak anisotropy and strong stray field cannot propagate until the magnetic field is large enough to overcome the pinning in cell phase. In contrast, at 700 K or above, the coercivity is controlled by the nucleation of reversed domain. Furthermore, it is found that the nucleation field of cell wall is larger than the corresponding anisotropy field, which is due to the strong exchange-coupled hardening by the cell phase.