Crystallographic transformations of rapidly quenched Sm10Fe90−xTix and magnetic properties of their nitrides

Abstract

Sm 10 Fe 90−x Ti x alloys (x=0, 1, 3, 4, 5, 6, 8, 10) were prepared by rapid quenching and sequent annealing. Structural transformations from amorphous, metastable-to-equilibrium phases, and magnetic properties of their nitrides were systematically investigated. A CaCu5-type metastable phase was formed for 0⩽x⩽10 as the crystallization of the amorphous alloys occurred below 700 °C. The CaCu5-type structure is transformed into a TbCu7-type one with increased annealing temperature (above 700 °C). These alloys have different structures including Th2Zn17 type for 0⩽x⩽3, TbCu7 type for 3<x<6, and ThMn12 type for 6⩽x⩽10, at high annealing temperatures (above 950 °C). Nitrogenation was carried out at 460 °C for 6 h. The best hard magnetic properties are obtained after nitriding for x=3. It gives Hc=17.6i kOe, 4πMr=7.7 kG, and (BH)max=6.8 MGOe for the TbCu7-type phase and Hc=8.6i kOe, 4πMr=8.4 kG, and (BH)max=10.2 MGOe for the CaCu5-type one. Although the coercivity of the CaCu5-type phase is lower than that of the TbCu7-type one, enhanced remanence of the former has been observed.