Pressure effect on magnetic susceptibility of LaCoO$_3$

TL;DR

This study investigates how hydrostatic pressure influences the magnetic susceptibility of LaCoO$_3$, revealing a significant negative and temperature-dependent pressure effect through experimental measurements and theoretical modeling.

Contribution

It combines precise experimental data with DFT+U calculations to analyze pressure effects on spin state energies in LaCoO$_3$, providing new insights into its magnetic behavior.

Findings

Pressure decreases magnetic susceptibility significantly.

The energy difference between spin states diminishes with volume expansion.

Temperature influences the spin state energy gap, predicting its vanishing near room temperature.

Abstract

The effect of pressure on magnetic properties of LaCoO$_3$ is studied experimentally and theoretically. The pressure dependence of magnetic susceptibility $\chi$ of LaCoO$_3$ is obtained by precise measurements of $\chi$ as a function of the hydrostatic pressure $P$ up to 2 kbar in the temperature range from 78 K to 300 K. A pronounced magnitude of the pressure effect is found to be negative in sign and strongly temperature dependent. The obtained experimental data are analysed by using a two-level model and DFT+U calculations of the electronic structure of LaCoO$_3$. In particular, the fixed spin moment method was employed to obtain a volume dependence of the total energy difference $\Delta$ between the low spin and the intermediate spin states of LaCoO$_3$. Analysis of the obtained experimental $\chi(P)$ dependence within the two-level model, as well as our DFT+U calculations, have revealed the anomalous large decrease in the energy difference $\Delta$ with increasing of the unit cell volume. This effect, taking into account a thermal expansion, can be responsible for the temperatures dependence of $\Delta$, predicting its vanishing near room temperature.