Magnetic and electric properties of double-perovskites and estimation of their Curie temperatures by ab initio calculations

TL;DR

This paper uses ab initio electronic structure calculations to estimate the Curie temperatures of various double perovskites, revealing systematic relationships with valence electrons and improving accuracy by considering oxygen interactions.

Contribution

It introduces a comprehensive ab initio approach to predict Curie temperatures in double perovskites, including methods to account for oxygen interactions and excited states.

Findings

Systematic correlation between valence electrons and Curie temperatures.

Improved Curie temperature estimates by including oxygen exchange interactions.

Validation of computational methods against experimental data.

Abstract

First principles electronic structure calculations have been carried out on ordered double perovskites Sr_2B'B"O_6 (for B' = Cr or Fe and B" 4d and 5d transition metal elements) with increasing number of valence electrons at the B-sites, and on Ba_2MnReO_6 as well as Ba_2FeMoO_6. The Curie temperatures are estimated ab initio from the electronic structures obtained with the local spin-density functional approximation, full-potential generalized gradient approximation and/or the LDA+U method (U - Hubbard parameter). Frozen spin-spirals are used to model the excited states needed to evaluate the spherical approximation for the Curie temperatures. In cases, where the induced moments on the oxygen was found to be large, the determination of the Curie temperature is improved by additional exchange functions between the oxygen atoms and between oxygen and B' and B" atoms. A pronounced systematics can be found among the experimental and/or calculated Curie temperatures and the total valence electrons of the transition metal elements.