Résumé:
This work intends to study from the first principles the structural stability, electronic,
magnetic and thermoelectric properties of the new hypothetical full-Heusler compounds
Mn2LiZ (Si, Ge, Sn, Al, Ga and In). We use the density functional theory implemented
by the linearized augmented plane wave method to perform structural optimization and
electronic structure calculations. As a main result, from the analysis of the total energies
of different systems, we find that the compounds with Z is Si, Ge, Al and Ga are structurally,
mechanically and thermodynamically more stable in the inverse Heusler structure
(XA structure). The electronic structure investigation shows that Mn2LiSi, Mn2LiGe and
Mn2LiSn are half-metallic ferrimagnetic with wide energy gaps and smaller total magnetic
moments. We obtain a spin gapless semiconductor and nearly spin semimetallic properties
with zero total spin moments in the Mn2LiAl and Mn2LiGa, respectively. The exchange
interactions are determined within the Korringa-Kohn-Rostoker Green’s function
framework. We show that the calculated inter-sublattice exchange interaction presents
a dominant contribution to the exchange. Having determined the exchange interactions,
we can deduce the Curie temperature in the mean-field approximation. Due to the large
values of the inter-sublattice exchange reactions, we find that the Curie temperature is
much higher than room temperature for all compounds, a prerequisite in spintronics. In
the present study, we also calculated and discussed the electronic transport properties
based on the semi-classical Boltzmann transport theory.
