High-Pressure Phase Diagram in the Manganites: a Two-site Model Study

TL;DR

This paper models the pressure dependence of the Curie temperature in manganites using a two-site double-exchange model, revealing that pressure-activated enhancement of superexchange interactions explains experimental observations.

Contribution

It introduces a theoretical two-site model incorporating electron-phonon coupling and superexchange to explain pressure effects on $T_C$ in manganites, aligning well with experiments.

Findings

Pressure-activated superexchange enhances antiferromagnetic interactions.

Model accurately reproduces experimental $T_C$ pressure dependence.

Jahn-Teller distortions alone do not account for $T_C$ behavior.

Abstract

The pressure dependence of the Curie temperature $T_C$ in manganites, recently studied over a wide pressure range, is not quantitatively accounted for by the quenching of Jahn-Teller distortions, and suggests the occurrence of a new pressure-activated localizing processes. We present a theoretical calculation of $T_C$ based on a two-site double-exchange model with electron-phonon coupling interaction and direct superexchange between the $% t_{2g}$ core spins. We calculate the pressure dependence of $T_C$ and compare it with the experimental phase diagram. Our results describe the experimental behavior quite well if a pressure-activated enhancement of the antiferromagnetic superexchange interaction is assumed.