Systematic analysis of structural and magnetic properties of spinel $CoB_2O_4$(B=Cr,Mn and Fe)compounds from their electronic structures

TL;DR

This study uses DFT+U calculations to analyze how changing the B cation in CoB2O4 spinels affects their structural and magnetic properties, revealing the importance of electron correlations and structural distortions.

Contribution

It provides a detailed electronic structure analysis of CoB2O4 spinels with different B cations, highlighting the effects of electron correlation and structural variations on their properties.

Findings

Electron-electron correlation is crucial for accurate ground state predictions.

Structural distortions significantly influence magnetic interactions.

Fe states are highly localized, affecting magnetic behavior.

Abstract

The structural and magnetic properties of spinel compounds $CoB_2O_4$ (B=Cr,Mn and Fe) are studied using the DFT+U method and generalized gradient approximation (GGA). We concentrate on understanding the trends in the properties of these materials as the B cation changes, in terms of relative strengths of crystal fields and exchange fields through an analysis of their electronic densities of states. We find that the electron-electron correlation plays a significant role in obtaining the correct structural and electronic ground states. Significant structural distortion in CoMn$_{2}$O$_{4}$ and "inverted" sublattice occupancy in CoFe$_{2}$O$_{4}$ affects the magnetic exchange interactions substantially. The trends in the magnetic exchange interactions are analysed in terms of the structural parameters and the features in their electronic structures. We find that the Fe states in CoFe$_{2}$O$_{4}$ are extremely localised, irrespective of the symmetry of the site, which makes it very different from the features of the states of the B cations in other two compounds. These results provide useful insights into the trends in the properties of CoB$_{2}$O$_{4}$ compounds with variation of B cation which would help in understanding the results of recent experiments on doping of Mn and Cr in multiferroic CoCr$_{2}$O$_{4}$.