Density functional theory study of vacancy induced magnetism in Li$_{3}$N

TL;DR

This study uses density functional theory to explore how lithium vacancies in alpha-Li3N induce long-range ferromagnetism within the material's layers, revealing the importance of vacancy location for magnetic properties.

Contribution

It provides a detailed theoretical analysis of vacancy-induced magnetism in alpha-Li3N, highlighting the role of vacancy position and concentration in magnetic behavior.

Findings

Long-range N(p)-ferromagnetism appears for vacancies within Li2N layers at x ≥ 0.7.

In-plane exchange couplings are the dominant magnetic interactions.

Vacancies substituting inter-plane Li cause structural collapse and do not induce magnetism.

Abstract

The effect of lithium vacancies in the hexagonal structure of $\alpha-$Li$_3$N, is studied within the framework of density functional theory. Vacancies ($\square$) substituting for lithium in $\alpha-$Li$_2$(Li$_{1-x}\square_x$)N are treated within the coherent potential approximation as alloy components. According to our results long range N($p$)-ferromagnetism ($\sim 1$ $\mu_B$) sets in for vacancy substitution within the [Li$_2$N] layers ($x \ge 0.7$) with no significant change in unit cell dimensions. By total energies differences we established that in-plane exchange couplings are dominant. Vacancies substituting inter-plane Li, leads to a considerable structural collapse ($c/a \approx 0.7$) and no magnetic moment formation.