Sr$_2$NbO$_4$: A $4d$ analogue of the layered perovskite Sr$_2$VO$_4$

TL;DR

This study investigates Sr$_2$NbO$_4$, a 4$d$ layered perovskite, revealing its stability, potential for 2D applications, and magnetic properties through advanced computational methods.

Contribution

It provides the first detailed theoretical analysis of Sr$_2$NbO$_4$, highlighting its stability, electronic structure, and magnetic interactions, which were previously unresolved.

Findings

Stable and exfoliable as a 2D material

Moderate mass renormalization indicating itinerant magnetism

Dominant in-plane ferromagnetic exchange with weak interlayer coupling

Abstract

This work focuses on the layered perovskite Sr$_2$NbO$_4$, a 4$d$ analogue of Sr$_2$VO$_4$, which remains an unsolved puzzle with a possible intriguing hidden magnetic order. Using density functional theory (DFT) calculations, we demonstrate the robust thermodynamic stability and exfoliability of Sr$_2$NbO$_4$, suggesting potential applications as a 2D material. Imperfect Fermi surface nesting indicates instabilities that may drive symmetry lowering, charge/orbital density waves, or superconductivity. Dynamical mean-field theory (DMFT) calculations reveal moderate mass renormalization $(m^*/m\sim1.3)$ and an itinerant character of magnetism with strong longitudinal spin fluctuations. The exchange interaction is dominated by in-plane ferromagnetic coupling with much weaker interlayer antiferromagnetic exchange.