Impurity metallic conduction below the critical concentration of Metal-Insulator Transition in Fe1-xCoxSi

TL;DR

This study investigates the metallic conduction behavior in Fe1-xCoxSi below the critical concentration for the metal-insulator transition, revealing impurity-driven effects on electronic and magnetic properties through detailed resistivity and thermoelectric measurements.

Contribution

The paper provides detailed analysis of resistivity and thermoelectric power in Fe1-xCoxSi, highlighting impurity electron effects and the semi-metallic ground state below the critical concentration.

Findings

Impurity electrons dominate properties below 35 K

System remains semi-metallic below critical concentration

Two-band model explains transport properties

Abstract

Analysis on very detailed measurements of resistivity ($ \rho $) and thermoelectric power (S) of magnetic impurity (Co) substituted iron silicide (FeSi) has been presented in this report. The impurity valence electrons of Co dominate the whole physical properties at low temperatures below 35 K, below the critical concentration x$_{c}$. The negative thermopower and the positive slope in the resistivity at low temperatures are exotic and show that the system is not entirely insulator below the critical concentration of MIT (x$_{c}$). So, due to the external impurity electrons, the system's magnetic ground state could change considerably compared to the parent compound FeSi. This report may help unveil the exotic nature of the ground state in the semi-metallic regime between x = 0 to x = 0.02. We have also explained the electrical and thermal transport properties using the two-band model.