Effect of substitution of Mn and Ga atoms by Fe atom in the Mn2GaC MAX phase

The magnetic properties of ordered and disordered MAX-phase Mn _2-xFe _2xGaC and Mn ₂Ga _1-xFe _xC (x = 12.5, 25, and 50 at.%) have been studied within DFT-GGA. The investigation of phase stability of M ₂ AX phases is performed by comparing the total energy of MAX phases to that of the set of competitive phases for calculation of the phase formation enthalpy. At the small concentration of Fe atoms (x = 12.5 %) compound remains stable. We have found that introducing Fe atom at A-site leads to the forming of ferromagnetic phase with large magnetic moments on magnetic atoms and magnetization. Through detailed group-theoretical analysis we have obtained that only ferromagnetic ordering is possible when Fe atom ordering over Ga sites. The study of exchange constants shows that the out-of-plane Fe-Mn exchange gives the main contribution in appearance of ferromagnetic phase. The temperature dependences of magnetization reveal the increase of Curie temperature in Mn ₂GaC with Fe atom incorporated into Ga-site.