Temperature dependence of coercivity in Sm2TM17 magnets and domain wall motion in magnetic materials

It was observed in Sm2TM17 magnets that decreasing Fe content did not stron gly affect room temperature coercivity but led to a significantly higher co ercivity at high temperatures; increasing Sm content resulted in much lower room temperature coercivity but substantially higher coercivity at high te mperatures; increasing Cu content led to higher coercivity at all temperatu res. In this paper, the effects of Fe, Sm, and Cu on coercivity are explain ed by using the temperature dependence of magnetocrystalline anisotropy of the 2 : 17 cell phase and 1 : 5 cell boundary phase. In order to explain co mplex temperature dependence of coercivity, thermal activation of domain wa lls must be taken into account. It is believed that the energy necessary fo r domain walls to overcome the energy barrier between the 1 : 5 cell bounda ry phase and 2 : 17 cell phase can be acquired not only from the magnetic H eld, but also from thermal energy k(B)T. This concept may apply to all magn etic materials in which domain wall motion is involved during magnetization and demagnetization processes.