Exchange Interaction and $T_c$ in Alkaline-earth-metal-oxide-based DMS without Magnetic Impurities: First Principle Pseudo-SIC and Monte Carlo Calculation

TL;DR

This study uses first-principles calculations and Monte Carlo simulations to explore how carbon doping induces and stabilizes ferromagnetism in alkaline-earth-metal-oxides, predicting Curie temperatures and exchange interactions.

Contribution

It demonstrates that accounting for electron self-interaction enhances the stability of C-induced ferromagnetism and clarifies the role of short-range exchange interactions in these materials.

Findings

C doping induces half-metallic ferromagnetism in alkaline-earth-metal-oxides.

Self-interaction correction stabilizes ferromagnetism and localizes C 2p states.

Curie temperature increases with C concentration in studied oxides.

Abstract

The prospects of half-metallic ferromagnetism being induced by the incorporation of C atoms into alkaline-earth-metal-oxides are investigated by the first principle calculation. The origin of the ferromagnetism is discussed through the calculation of the electronic structure and exchange coupling constant by using the pseudo-potential-like self-interaction-corrected local spin density method. The Curie temperature ($T_c$) is also predicted by employing the Monte Carlo simulation. It is shown that by taking the electron self-interaction into account, the half-metallic ferromagnetism induced by C in the host materials is more stabilized in comparison with the standard LDA case, and the C's $2p$ electron states in the bandgap become more localized resulting in the predominance of the short-ranged exchange interaction. While the ferromagnetism in MgO$_{1-x}$C$_x$ is stabilized due to the exchange interaction of the $1st$-nearest neighbor pairs and might be suppressed by the anti-ferromagnetic super-exchange interaction at higher $x$, the ferromagnetism in CaO$_{1-x}$C$_x$, SrO$_{1-x}$C$_x$, and BaO$_{1-x}$C$_x$ is stabilized by both the $1st$- and $2nd$-nearest neighbor pairs, and $T_c$ monotonously increases with the C concentration.