Temperature dependence of coercivity in Sm/sub 2/TM/sub 17/ magnets and domain wall motion in magnetic materials

Abstract

It was observed in Sm/sub 2/TM/sub 17/ magnets that decreasing Fe content did not strongly affect room temperature coercivity but led to a significantly higher coercivity at high temperatures; increasing Sm content resulted in much lower room temperature coercivity but substantially higher coercivity at high temperatures; increasing Cu content led to higher coercivity at all temperatures. In this paper, the effects of Fe, Sm, and Cu on coercivity are explained by using the temperature dependence of magnetocrystalline anisotropy of the 2:17 cell phase and 1:5 cell boundary phase. In order to explain complex temperature dependence of coercivity, thermal activation of domain walls must be taken into account. It is believed that the energy necessary for domain walls to overcome the energy barrier between the 1:5 cell boundary phase and 2:17 cell phase can be acquired not only from the magnetic field, but also from thermal energy k/sub B/T. This concept may apply to all magnetic materials in which domain wall motion is involved during magnetization and demagnetization processes.