Etude des propri et es electroniques et magn etiques de l'alliage Half-Heusler NiMnSb

Abstract

In this Master's thesis in materials physics, we present an ab-initio study of the electronic and magnetic properties of the NiMnSb compounds, using the PseudoPotentials - Planar Wave (PP-PW) method. This is implemented in the CASTEP code and based on the Functional Theory of Density (DFT). The exchange-correlation e ect was processed by the Generalized Gradient Approximation (GGAPBEsol), taking into account the two spin states. The geometrical optimization was carried out for a pressure range varying between -16 and 50 GPa. The resulting compression module indicates that NiMnSb is very resistant to volume changes. The analysis of the electronic structures reveals that the semi-Heusler NiMnSb alloy behaves like a ferromagnetic demi-metal. The pressure e ect was important on the electronic properties, resulting in a large variation in spin polarization. The magnetic moment obtained is typically an integer value and follows the Slater-Pauling curve. Magnetic properties were investigated under pressure.