Doping driven magnetic instabilities and quantum criticality of NbFe$_{2}$

TL;DR

This study uses density functional theory to explore how doping affects the magnetic phases and quantum criticality in NbFe$_{2}$, highlighting the roles of non-rigid-band effects, disorder, and Fermi surface nesting.

Contribution

It provides a detailed theoretical analysis of magnetic instabilities and phase evolution in NbFe$_{2}$ due to doping, emphasizing the importance of non-rigid-band effects and Fermi surface features.

Findings

Fermi surface nesting drives finite q antiferromagnetism.

Total energy calculations favor q=0 antiferromagnetism as the ground state.

Doping influences magnetic phases through non-rigid-band effects and disorder.

Abstract

Using density functional theory we investigate the evolution of the magnetic ground state of NbFe$_{2}$ due to doping by Nb-excess and Fe-excess. We find that non-rigid-band effects, due to the contribution of Fe-\textit{d} states to the density of states at the Fermi level are crucial to the evolution of the magnetic phase diagram. Furthermore, the influence of disorder is important to the development of ferromagnetism upon Nb doping. These findings give a framework in which to understand the evolution of the magnetic ground state in the temperature-doping phase diagram. We investigate the magnetic instabilities in NbFe$_{2}$. We find that explicit calculation of the Lindhard function, $\chi_{0}(\mathbf{q})$, indicates that the primary instability is to finite $\mathbf{q}$ antiferromagnetism driven by Fermi surface nesting. Total energy calculations indicate that $\mathbf{q}=0$ antiferromagnetism is the ground state. We discuss the influence of competing $\mathbf{q}=0$ and finite $\mathbf{q}$ instabilities on the presence of the non-Fermi liquid behavior in this material.