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.