Magnetism from $2p$ States in Alkaline Earth Monoxides: Trends with Varying N Impurity Concentration

TL;DR

This study investigates how nitrogen impurities induce magnetism in alkaline earth monoxides, revealing that magnetic coupling depends on impurity localization and concentration, with potential for magnetic ordering in specific lattice arrangements.

Contribution

It provides a detailed analysis of nitrogen-induced magnetism in alkaline earth monoxides using density functional methods, highlighting the effects of impurity localization and Coulomb interactions.

Findings

Magnetic moments are localized near N$^{2-}$ ions.

Magnetic coupling is strong in the itinerant limit, weaker when localized.

Ordering on a cubic sublattice may enhance magnetic interactions.

Abstract

$2p$-based magnetic moments and magnetic coupling are studied with density functional based methods for substitutional N in the alkaline earth monoxide series MgO, CaO, SrO, BaO. The hole is rather strongly localized near the N$^{2-}$ ion, being somewhat more so when strong on-site interactions are included in the calculations. Strong magnetic coupling is obtained in the itinerant electron limit but decreases strongly in the localized limit in which the Coulomb repulsion within the N $2p$ shell (U) is much greater than the N $2p$ impurity bandwidth (W). We find that this limit is appropriate for realistic N concentrations. Ordering on a simple cubic sublattice may maximize the magnetic coupling due to its high directionality.