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

摘要

The prospects of half-metallic ferromagnetism being induced by theincorporation of C atoms into alkaline-earth-metal-oxides are investigated bythe first principle calculation. The origin of the ferromagnetism is discussedthrough the calculation of the electronic structure and exchange couplingconstant by using the pseudo-potential-like self-interaction-corrected localspin density method. The Curie temperature ($T_c$) is also predicted byemploying the Monte Carlo simulation. It is shown that by taking the electronself-interaction into account, the half-metallic ferromagnetism induced by C inthe 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 resultingin the predominance of the short-ranged exchange interaction. While theferromagnetism in MgO$_{1-x}$C$_x$ is stabilized due to the exchangeinteraction of the $1st$-nearest neighbor pairs and might be suppressed by theanti-ferromagnetic super-exchange interaction at higher $x$, the ferromagnetismin CaO$_{1-x}$C$_x$, SrO$_{1-x}$C$_x$, and BaO$_{1-x}$C$_x$ is stabilized byboth the $1st$- and $2nd$-nearest neighbor pairs, and $T_c$ monotonouslyincreases with the C concentration.