Magnetism in Sr$_{2}$CrMoO$_{6}$: A combined abinitio and model study

TL;DR

This study combines first-principles DFT calculations and model analysis to understand the magnetic properties of Sr$_2$CrMoO$_6$, revealing how charge transfer energy influences hybridization and magnetic transition temperature.

Contribution

It provides a detailed microscopic analysis of Sr$_2$CrMoO$_6$'s magnetism, highlighting the role of charge transfer energy and superexchange, and compares it with related compounds.

Findings

Charge transfer energy suppresses Cr-Mo hybridization.

Magnetic transition temperature remains high due to superexchange.

Additional Mo moments contribute to magnetism.

Abstract

Using a combination of first-principles density functional theory (DFT) calculations and exact diagonalization studies of a first-principles derived model, we carry out a microscopic analysis of the magnetic properties of the half-metallic double perovskite compound, Sr$_2$CrMoO$_6$, a sister compound of the much discussed material Sr$_2$FeMoO$_6$. The electronic structure of Sr$_2$CrMoO$_6$, though appears similar to Sr$_2$FeMoO$_6$ at first glance, shows non trivial differences with that of Sr$_2$FeMoO$_6$ on closer examination. In this context, our study highlights the importance of charge transfer energy between the two transition metal sites. The change in charge transfer energy due to shift of Cr $d$ states in Sr$_2$CrMoO$_6$ compared to Fe $d$ in Sr$_2$FeMoO$_6$ suppresses the hybridization between Cr $t_{2g}$ and Mo $t_{2g}$. This strongly weakens the hybridization-driven mechanism of magnetism discussed for Sr$_2$FeMoO$_6$. Our study reveals that, nonetheless, the magnetic transition temperature of Sr$_2$CrMoO$_6$ remains high since additional superexchange contribution to magnetism arises with a finite intrinsic moment developed at the Mo site. We further discuss the situation in comparison to another related double perovskite compound, Sr$_2$CrWO$_6$. We also examine the effect of correlation beyond DFT, using dynamical mean field theory (DMFT).