First-principles study of anomalous thermoelectric effect in CoMSb(M=Sc, Ti, V, Cr, Mn)

The half-Heusler alloys, intermetallics with face-centered cubic crystal structure and chemical composition of XYZ, exhibit many peculiar properties, such as half- metallic ferromagnetic state and large thermoelectric effect. It is well known that the half-Heusler alloys are good thermoelectrics exhibiting large Seebeck effect originating from its narrow gap semiconducting state with 18 valence electron counts per formula unit. Recently, the anomalous Nernst effect (ANE) has attracted attention as a new thermoelectric generation mechanism and the large ANE was reported experimentally in the Heusler alloy Mn₃Sn [1]. In this work, we focused on carrier-dependence of thermoelectric properties including ANE in half-Heusler alloys. We have performed first-principles computations on half-Heusler alloys CoMSb (M=Sc, Ti, V, Cr, Mn) and found that the crystal-momentum component of effective magnetic field generates large ANE when the chemical potential is properly tuned. This behavior was clearly understood by the energy-dependent anomalous Hall conductivity. [1] M. Ikhlas, T. Tomita, T. Koretsune, M. Suzuki, N. Daisuke, R. Arita, Y. Otani, and S. Nakatsuji, Nat. Phys (2017).