Theoretical investigation into the possibility of very large moments in Fe16N2

TL;DR

This study uses advanced first-principles computational methods to investigate the magnetic properties of Fe16N2, aiming to clarify the possibility of very large magnetic moments in this phase.

Contribution

It provides a comprehensive theoretical analysis employing hybrid functionals, GW, and GGA+U methods with cRPA-calculated parameters to assess magnetic moments in Fe16N2.

Findings

Hybrid functional yields a 2.9 μ_B moment per Fe.

GW approximation yields a 2.6-2.7 μ_B moment per Fe.

GGA+U with cRPA parameters yields a 2.7 μ_B moment per Fe.

Abstract

We examine the mystery of the disputed high-magnetization \alpha"-Fe16N2 phase, employing the Heyd-Scuseria-Ernzerhof screened hybrid functional method, perturbative many-body corrections through the GW approximation, and onsite Coulomb correlations through the GGA+U method. We present a first-principles computation of the effective on-site Coulomb interaction (Hubbard U) between localized 3d electrons employing the constrained random-phase approximation (cRPA), finding only somewhat stronger on-site correlations than in bcc Fe. We find that the hybrid functional method, the GW approximation, and the GGA+U method (using parameters computed from cRPA) yield an average spin moment of 2.9, 2.6 - 2.7, and 2.7 \mu_B per Fe, respectively.