Thermal decomposition of ThMn12-type phase and its optimum stabilizing elements in SmFe12-based alloys

We investigated the phase stability of SmFe12-based compounds by experimental and computational first-principles approaches. The effect of particle size and alloy composition on the thermal decomposition rate is addressed. We show that decomposition begins with Sm evaporation from particle surface, resulting in the formation of α-Fe and Fe2Ti phases. The decomposition rate scales inversely with particle size. A significant stabilizing effect can be realized by substituting Fe with phase stabilizing elements such as V or Ga. According to ab initio calculations, Ti, V, and Ga lower the formation energies. However, when the reduction in magnetic moment is considered, the most effective stabilizing element that can minimize the reduction of μ0M is Ga. These findings present a useful insight on the potential solutions for the development of bulk Sm(Fe0·8Co0.2)12-based magnets. •The phase stability of SmFe12-based compounds are investigated.•Decomposition begins with Sm evaporation from particle surface and its rate scales inversely with particle size.•The most effective stabilizing element with minimum reduction of μ0Ms is Ga.