Stability, magnetic, and electronic properties of L21 and B2 phases in Co2MnAl Heusler alloy

Using first-principles density functional theory based method we have investigated the stability, magnetic, and electronic properties of L21 and B2 phases in Co2MnAl Heusler alloy. The spin polarizations as well as the magnetizations are stable against small tetragonal distortions. The calculated Curie temperature TC of the L21 phase is 789 K which is about 60 K higher than that (TC = 723 K) of the B2 phase. The total magnetic moments of L21 and B2 phases under GGA scheme are about 4 μB in agreement with the experimental value while the moments under GGA + U scheme have large values and are very sensitive to the U parameter. Electronic structure calculations show that there is a energy gap in the minority spin states in the L21 phase and the gap disappears in the B2 phase. Not only the L21 phase but also the B2 phase exhibits relatively high values of the spin polarization ratio P as very low density of states at the Fermi level in the minority spin band. Our results agree with available experimental results.