Electronic and Vibrational Properties of Fe2NiAl and Co2NiAl Full Heusler Alloys: A First-Principles Comparison

<p>In this work, we report on a systematic first-principles study of the structural, electronic, vibrational and thermodynamic properties of the cubic Fe₂NiAl and tetragonally distorted Co₂NiAl full Heusler compounds. We discuss systematically the competition between the inverse Heusler structure and a T<i>^p</i>-type layered atomic ordering formed by the alternating planes of (Fe,Co) and Ni atoms in terms of the electronic and vibrational density of states.</p> <p>Such an arrangement is predicted to be the ground state of Fe₂NiAl. For Co₂NiAl, layered ordering has slightly higher energy in comparison with the inverse one, however, we show that it might be stabilized at rather low temperatures.</p> <p> </p> <p>Due to the broken symmetry, layered T<i>^p</i>-Fe₂NiAl possesses a large MAE of the same order as tetrataenite FeNi - even in a phase with cubic lattice parameters, which makes a T<i>^p</i>-type layered order an interesting feature for rare-earth free permanent magnets in Heusler-type compounds.</p>