First principles study of the electronic and magnetic structures of the tetragonal and orthorhombic phases of Ca3Mn2O7

TL;DR

This study uses density functional theory to analyze the electronic and magnetic properties of Ca3Mn2O7's orthorhombic and tetragonal phases, revealing stability and magnetic ordering differences.

Contribution

It provides a detailed first-principles comparison of the electronic and magnetic structures of Ca3Mn2O7's phases, including spin exchange interactions and stability analysis.

Findings

Orthorhombic phase is more stable than tetragonal.

Orthorhombic phase is antiferromagnetic.

Magnetic insulating states are more stable than metallic states.

Abstract

On the basis of density functional theory electronic band structure calculations using the augmented spherical wave method, the electronic and magnetic properties of the orthorhombic and tetragonal phases of Ca3Mn2O7 were investigated and the spin exchange interactions of the orthorhombic phase were analyzed. Our calculations show that the magnetic insulating states are more stable than the non-magnetic metallic state for both polymorphs of Ca3Mn2O7, the orthorhombic phase is more stable than the tetragonal phase, and the ground state of the orthorhombic phase is antiferromagnetic. The total energies calculated for the three spin states of the orthorhombic phase of Ca3Mn2O7 led to estimates of the spin exchange interactions Jnn = -3.36 meV and Jnnn = -0.06 meV. The accuracy of these estimates were tested by calculating the Curie-Weiss temperature within the mean-field approximation.