Understanding the temperature and pressure dependent electronic properties of FeSi: DFT+DMFT study

Abstract

Electronic structures of FeSi and Fe$_{1.02}$Si$_{0.98}$ under pressure (achieved through volume compression) have been investigated by using DFT+DMFT and KKR-CPA methods, respectively. The widening of band-gap with increasing pressure suggests that the experimentally observed insulator to metal transition temperature should shift towards the higher temperature for FeSi. KKR-CPA calculations have shown the presence of impurity states in the gapped region which predicts the half-metallic nature. The closure of gap (in one spin channel) with pressure increment appears to be responsible for experimentally observed semiconductor to metal transition in Fe excess samples at a temperature below 50 K. Magnetic moments at Fe excess sites are found to be decreasing with increasing pressure from 2.4 $\mu_B$ per Fe atom (612 Bohr$^3$) to 1.2 $\mu_B$ per Fe atom (507 Bohr$^3$). Moreover, for FeSi the calculated local spin susceptibility has shown decreasing behavior with pressure rise similar to experimental result.