The magnetization behavior and magnetic viscosity of Sm(Co, Fe, Cu, Zr)Z ribbons with different temperature dependence of coercivity

Two types of Sm(Co, Fe, Cu, Zr)(Z) ribbons with different temperature dependence of coercivity are investigated in comparison at different temperatures. It is found that their magnetization behaviors and magnetic viscosity are distinctly different. The magnetization of sample A (with abnormal temperature dependence of coercivity) behaves as a single phase permanent magnet at room temperature, and then becomes similar to a nanocomposite magnet with the increase of temperature. However, sample B (with negative temperature coefficient of coercivity) is similar to a nanocomposite magnet at the whole temperature range. The magnetic viscosity is mainly determined by the irreversible magnetization for both ribbons, while there emerges an extra small peak of magnetic viscosity coefficient S(H) at low field and high temperature for sample B. The different content and distribution of Cu in the cell boundary phase are proposed to be responsible for the differences of temperature dependence of coercivity, magnetization, and magnetic viscosity behaviors of these two types of Sm (Co, Fe, Cu, Zr)(Z) ribbons. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3334540]