Structural properties and large coercivity of bulk Mn3−xGa (0 ≤ x ≤ 1.15)

The tetragonal DO22 phase of the Mn3−xGa compounds, with x varying from 0 to 1.15, has been successfully synthesized by annealing the ingots with the cubic γ-phase. It is found that the lattice parameter a of the tetragonal cell remains almost constant, while the lattice parameter c increases significantly as x varies from 0 to 1.15. In the meantime, the magnetization of Mn3−xGa (at 7 T) increases dramatically with increasing x. A substitution model, which is different to the model with manganese vacancies, is proposed to explain these changes. According to this model, the increase of the lattice parameter c and the magnetization with x can be explained by an assumption that Mn atoms at 2b sites are preferentially substituted by larger and nonmagnetic Ga atoms. A coercivity which is higher than that of other bulk Mn3−xGa alloys ever reported is achieved. Coercivities as large as iHc = 21.4 kOe and 18.2 kOe are obtained for Mn3.0Ga at 5 K and 300 K, respectively