Pressure-induced magnetic moment abnormal increase in Mn 2 FeAl and non-continuing decrease in Fe 2 MnAl via first principles

The magnetism of Fe 2 MnAl and Mn 2 FeAl compounds are studied by first principles. Evolutions of magnetic moment of Fe 2 MnAl display distinct variation trends under pressure, showing three different slopes at different pressure intervals, 0~100 GPa, 100~250 GPa, 250–400 GPa, respectively, and the moment collapses finally at 450 GPa. The magnetic moment of Mn 2 FeAl shows an increasing tendency below 40 GPa and decreases subsequently with pressure, and collapses ultimately at about 175 GPa. Such non-continuing decrease of Fe 2 MnAl originates from the unusual charge transfer of Fe and Mn and bond populations rearrangement of Fe-Fe and Mn-Fe, whereas the distinct moment evolution of Mn 2 FeAl is attributed to the complicated distributions of bond populations. The half-metallicity of the compounds can be maintained at low pressure, below about 100 GPa in Fe 2 MnAl and 50 GPa in Mn 2 FeAl. The magnetic moment collapse process didn’t induce volume and bond length anomalies in the two compounds, the unique anomaly is the elastic softening behaviour in elastic constant c 44 and shear ( G ) and Young’s ( E ) moduli of Fe 2 MnAl at 270 GPa, where the second moment collapse occurs.