Hund's coupling driven nature of magnetism in negative charge transfer material, $\mathrm{SrCoO_3}$

TL;DR

This study uses dynamical mean-field theory to reveal that Hund's coupling significantly influences the magnetic properties and electronic correlations in SrCoO3, including quasiparticle mass enhancement and the collapse of ferromagnetism at high temperatures.

Contribution

It demonstrates that Hund's physics governs the magnetism and correlation effects in SrCoO3, providing a microscopic understanding through advanced theoretical modeling.

Findings

Magnetic transition temperature T_c ~ 350 K matches experiments.

Quasiparticle mass enhancement up to 7 times for Co 3d states.

Collapse of ferromagnetism driven by Stoner-like exchange splitting reduction.

Abstract

In this work, we investigate the microscopic origin of magnetism in $\mathrm{SrCoO_3}$ by incorporating electronic correlations within the dynamical mean-field theory (DMFT) framework. We note a remarkable agreement of the calculated magnetic observables ( saturation magnetization $\sim$2.4 $\mu_B$; magnetic transition temperature, $T_c$$\sim$350 K) with the experimental results. The system exhibits Hund's coupling-induced strong quasiparticle mass enhancements of upto $m^*/m$ $\sim$7 for Co 3$d$ states, with the largest renormalization occurring in the majority spin $t_{2g}$ orbitals, marking the onset of orbital-selectivity. Our results reveal a Stoner-$like$ collapse of exchange splitting that drives the loss of long-range ferromagnetic order at $T_c$. The breakdown of Fermi-liquid behavior down to $T$$\sim$100 K suggests a suppressed coherence scale. Local magnetic moment originates from a mixed-spin configuration formed through dynamical fluctuation between intermediate-spin and high-spin states. Large charge fluctuations ($\langle$$\Delta$N$^2$$\rangle$$\sim$0.6) together with heavy quasiparticles establish the correlation effects regime, governed predominantly by Hund's physics in $\mathrm{SrCoO_3}$.