The effects of CNTs and/or Si additions on the structure and magnetic properties of SmCo7-based alloys

Abstract

In this work, SmCo7, SmCo7(CNTs)0.05, SmCo6.1Si0.9, SmCo6.1Si0.9(CNTs)0.05 as-cast ingots and ribbons were prepared by arc-melting and melt-spinning methods respectively. The effects of Si and/or CNTs additions on the structure and magnetic properties of SmCo7-based alloys were investigated. It was found that adding Si into the SmCo7-based as-cast alloys can stabilize the TbCu7-type structure, while CNTs addition facilitates the formation of Th2Zn17-type phase. However, for SmCo7-based ribbons, the cooling rate plays a more significant role in the formation of a single TbCu7-type phase than the doped elements. The coercivity (Hc) and remanence ratio (Mr/M2T) of all SmCo7-based ribbons increase with the addition of CNTs and/or Si. In particular, simultaneous addition of CNTs and Si can improve the Hc and Mr/M2T more effectively than that of a single one. On the other hand, the magnetization of SmCo7-based ribbons at high temperature is improved by CNTs addition while decreased by Si addition. At the same time, the thermal stability of ribbons decreases when Si is introduced. The possible mechanism of magnetization reversal in the SmCo7-based ribbons containing Si and/or CNTs is considered to be the combination of nucleation and pinning.