The arising of ferromagnetism in Al-doped Mn2(Ga1-xAlx)C MAX phases

https://doi.org/10.1016/j.jmmm.2024.172193

The magnetic properties of ordered MAX phases Mn₂(Al_xGa_1−x)C (x = 0.125, 0.25, 0.5, 0.75 and 0.875) have been studied within the DFT-GGA. We have found that increase of Al atom at A-site leads to the formation of the ferromagnetic phase with large magnetization of about 3.6 μ_B/f.u. The investigation of the phase stability is performed by comparing the total energy of the MAX phases with that of a set of competitive phases for calculation of the phase formation enthalpy. Up to a concentration of Al atoms x = 0.7 the compound remains thermodynamically stable. The exchange constants analysis shows the crucial role of exchange interactions between manganese atoms along the c-axis in forming of ferromagnetism. The magnetic transition temperature of Mn₂(Al_xGa_1−x)C alloys increases with increase of the aluminum concentration.