The influence of the rare earth ions radii on the Low Spin to Intermediate Spin state transition in lanthanide cobaltite perovskites: LaCoO3 vs. HoCoO3

TL;DR

This study uses first principles calculations to analyze how the ionic radii of rare earth ions affect the spin state transition in lanthanide cobaltite perovskites, revealing a higher transition temperature in HoCoO3 due to stronger crystal field splitting.

Contribution

It provides a detailed first-principles analysis of the spin state transition in LaCoO3 and HoCoO3, highlighting the role of ionic radii and crystal field effects in these materials.

Findings

HoCoO3 has a higher spin transition temperature than LaCoO3.

Smaller ionic radius of Ho leads to stronger crystal field splitting.

The spin transition involves competition between crystal field splitting and exchange interactions.

Abstract

We present first principles LDA+U calculations of electronic structure and magnetic state for LaCoO3 and HoCoO3. Low Spin to Intermediate Spin state transition was found in our calculations using experimental crystallographic data for both materials with a much higher transition temperature for HoCoO3, which agrees well with the experimental estimations. Low Spin state t6e0 (non-magnetic) to Intermediate Spin state t5e1 (magnetic) transition of Co(3+) ions happens due to the competition between crystal field t_2g-e_g splitting and effective exchange interaction between 3$d$ spin-orbitals. We show that the difference in crystal structure parameters for HoCoO3 and LaCoO3 due to the smaller ionic radius of Ho ion comparing with La ion results in stronger crystal field splitting for HoCoO3 (0.09 eV ~ 1000 K larger than for LaCoO3) and hence tip the balance between the Low Spin and Intermediate Spin states to the non-magnetic solution in HoCoO3.