Violation of the Rule of Parsimony: Mixed Local Moment and Itinerant Fe Magnetism in Fe$_{3}$GeN

TL;DR

This study reveals that minor structural distortions in Fe$_3$GeN cause a split in Fe magnetic behavior, demonstrating the material's magnetic flexibility and potential for tunable magnetic properties through structural or chemical modifications.

Contribution

First principles calculations uncover the coexistence of local moment and itinerant magnetism in Fe$_3$GeN due to structural distortion, highlighting a new mechanism for magnetic tunability.

Findings

Fe$_3$GeN exhibits distinct magnetic behaviors at different Fe sites.

Minor structural changes can dramatically alter magnetic properties.

Potential for tuning magnetism via chemical or strain control.

Abstract

Ternary iron nitrides are of considerable interest due to their diverse magnetic properties. We find, based on first principles calculations, that the relatively minor structural distortion from the cubic antiperovskite structure in Fe$_3$GeN leads to unusual magnetic behavior. In particular, there is a separation into Fe sites with very different magnetic behaviors, specifically a site with Fe atoms having a stable local moment and a site where the Fe shows characteristics of much more itinerant behavior. This shows a remarkable flexibility of the Fe magnetic behavior in these nitrides and points towards the possibility of systems where minor structural and chemical changes can lead to dramatic changes in magnetic properties. The results suggest that, analogously to oxide perovskite materials, modulation of magnetic properties via chemical or strain control of octahedral rotation may be feasible. This may then lead to approaches for tuning magnetism to realize properties of interest, for example tuning magnetic transitions to quantum critical regimes or to proximity to metamagnetic transitions of interest for devices.