First-Principles Investigation of the Influence of Disorder on Electronic and Magnetic Properties in CoFeMnAl Quaternary Heusler Alloys

Abstract

First-principles calculations, combined with the supercell approach, are employed to investigate the effects of atomic disorder on the electronic properties of the CoFeMnAl quaternary Heusler alloy (LiMgPdSn-type). The ordered alloy is a half-metallic ferromagnet; its moment obeys the Slater-Pauling rule with T_C > 300 K. We analyse twelve antisite and six swap disorder configurations. Calculations show that the Fe_Mn antisite is the most energetically favourable defect (−1.25 eV), followed by the FeCo antisite and the MnAl swap. The disorder generally contracts the spin-down gap. Half-metallicity is largely preserved but completely lost for Co_Al, Co_Mn antisite and CoAl, CoMn swap defects. Disorder has a significant effect on the magnetic moment and Curie temperature. The Fe_Mn antisite gives 3.12 µ_B, which is very close to the experimental value of 3.10 µ_B. This study demonstrates the importance of considering disorder when predicting the properties of Heusler alloys.