Simulation of the enhanced Curie temperature in Mn_5Ge_3C_x compounds

TL;DR

This paper combines first principles calculations and Monte Carlo simulations to demonstrate that carbon doping significantly enhances the Curie temperature in Mn_5Ge_3C_x compounds by strengthening ferromagnetic interactions.

Contribution

It provides the first detailed theoretical analysis explaining the electronic and magnetic mechanisms behind the Curie temperature enhancement due to carbon doping.

Findings

Enhanced Curie temperature in Mn_5Ge_3C_x confirmed by simulations

Carbon doping strengthens ferromagnetic Mn-Mn interactions

Electronic effects primarily drive the Curie temperature increase

Abstract

Mn_5Ge_3C_x films with x>0.5 were experimentally shown to exhibit a strongly enhanced Curie temperature T_C compared to Mn_5Ge_3. In this letter we present the results of our first principles calculations within Green's function approach, focusing on the effect of carbon doping on the electronic and magnetic properties of the Mn_5Ge_3. The calculated exchange coupling constants revealed an enhancement of the ferromagnetic Mn-Mn interactions mediated by carbon. The essentially increased T_C in Mn_5Ge_3C is well reproduced in our Monte Carlo simulations and together with the decrease of the total magnetisation is found to be predominantly of an electronic nature.