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

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 $\mathrm{SrCoO_3}$.