Density Functional Study of Excess Fe in Fe$_{1+x}$Te: Magnetism and Doping

TL;DR

This study uses density functional theory to explore how excess Fe in Fe$_{1+x}$Te influences its electronic and magnetic properties, revealing electron doping and strong magnetism that impact superconductivity.

Contribution

It provides new insights into the valence state and magnetic behavior of excess Fe, highlighting its role in electron doping and local moment formation in Fe$_{1+x}$Te.

Findings

Excess Fe has valence near Fe$^{+}$, providing electron doping.

Excess Fe is strongly magnetic, creating local moments.

These magnetic effects persist even when plane magnetism is suppressed.

Abstract

The electronic and magnetic properties of the excess Fe in iron telluride Fe$_{(1+x)}$Te are investigated by density functional calculations. We find that the excess Fe occurs with valence near Fe$^{+}$, and therefore provides electron doping with approximately one carrier per Fe, and furthermore that the excess Fe is strongly magnetic. Thus it will provide local moments that interact with the plane Fe magnetism, and these are expected to persist in phases where the magnetism of the planes is destroyed for example by pressure or doping. These results are discussed in the context of superconductivity.