Structural stability, electronic, magnetic and thermoelectric properties for half-metallic quaternary Heusler alloys CrLaCoZ

Using first-principles calculations, we predict the CrLaCoZ (Z = Al, Ga, In, Ge, Sn, Pb) Heusler alloys to be half-metals, and their total magnetic moments follow the Slater-Pauling rule M-t = Z(t) - 18. Structural stability is estimated in terms of thermodynamics, dynamic, mechanical and thermal. A comparison in total energy shows that the CrLaCoZ alloys have ferrimagnetic ground states, and the competition between d-d exchange, super-exchange and RKKY exchange interactions leads to the appearance of magnetic order phase. Phase separation shows that CrLaCoAl, CrLaCoGa, CrLaCoIn and CrLaCoSn are easier to be synthesized in experiment. The formation of half-metallic gap ascribes to the d-d, p-d orbital hybridizations. Furthermore, we find that the magnitude of gap is decided by the strength of exchange splitting between e(g) and t(2g) states according the distribution and occupation of electronic states. Presence of X and DO3 disorders destroys their half-metallicity. In addition, we examine the effects of spin-orbit coupling on electronic structure, and calculate their thermoelectric properties by using Boltzmann transport theory. From the calculated exchange interactions, it is found that the Cr (A)-Cr(A), Cr(A)-La(B) and Cr(A)-Co(C) exchanges play a leading role in all interactions, and finally determine the Curie temperatures. Apart from the CrLaCoSn alloy, other alloys have evidently higher Curie temperatures than room temperature, which is favorable as an electrode materials in magnetic tunnel junction.

Automated summary

Using first-principles calculations, the CrLaCoZ (Z = Al, Ga, In, Ge, Sn, Pb) Heusler alloys are predicted to be half-metals. The structural stability of these alloys is analyzed in terms of various factors, and it is found that CrLaCoAl, CrLaCoGa, CrLaCoIn, and CrLaCoSn are easier to synthesize experimentally. The formation of a half-metallic gap is attributed to the hybridization of d-d and p-d orbitals, while the presence of impurities destroys their half-metallicity. Additionally, the effects of spin-orbit coupling on electronic structure and the thermoelectric properties of these alloys are investigated.