Magnetism in 2D BN$_{1-x}$O$_x$ and B$_{1-x}$Si$_x$N: polarized itinerant and local electrons

TL;DR

This study uses first-principles calculations to explore how doping 2D BN with oxygen or silicon induces various magnetic phases, revealing the conditions for polarized itinerant electrons and their stability.

Contribution

It identifies distinct magnetic phases in doped 2D BN and analyzes the conditions for polarized itinerant electrons, highlighting differences between oxygen and silicon doping effects.

Findings

Oxygen doping induces all three magnetic phases including polarized itinerant electrons.

Silicon doping does not lead to polarized itinerant electrons but shows other magnetic phases.

The stability of the polarized itinerant phase depends on dopant distribution and applied strain.

Abstract

We use density functional theory based first-principles methods to study the magnetism in a 2D hexagonal BN sheet induced by the different concentrations of oxygen and silicon atoms substituting for nitrogen (O$_\mathrm{N}$) and boron (Si$_\mathrm{B}$) respectively. We demonstrate the possible formation of three distinct phases based on the magnetization energy calculated self-consistently for the ferromagnetic (ME$_{\mathrm{FM}}$) and antiferromagnetic (ME$_{\mathrm{AFM}}$) states, i.e. the paramagnetic phase with ME$_{\mathrm{FM}}$=ME$_{\mathrm{AFM}}$, the ferromagnetic phase with ME$_{\mathrm{FM}}$$>$ME$_{\mathrm{AFM}}$ and finally the polarized itinerant electrons with finite ME$_{\mathrm{FM}}$ but zero ME$_{\mathrm{AFM}}$. While the O$_\mathrm{N}$ system was found to exist in all three phases, no tendency towards the formation of the polarized itinerant electrons was observed for the Si$_\mathrm{B}$ system though the existence of the other two phases was ascertained. The different behavior of these two systems is associated with the diverse features in the magnetization energy as a function of the oxygen and silicon concentrations. Finally, the robustness of the polarized itinerant electron phase is also discussed with respect to the O substitute atom distributions and the applied strains to the system.