What drives the charge/orbital ordering in La0.5Sr1.5MnO4: Jahn-Teller distortion versus orbital ordering

TL;DR

This study investigates the mechanisms behind charge and orbital ordering in La0.5Sr1.5MnO4, showing that orbital order, rather than Jahn-Teller distortion, primarily drives the metal-insulator transition.

Contribution

It provides experimental evidence that orbital ordering, not Jahn-Teller distortions, is the main factor influencing the phase transition in La0.5Sr1.5MnO4.

Findings

Orbital order parameter increases gradually with temperature.

Orbital ordering dominates over Jahn-Teller effects.

Orbital-orbital exchange interactions are more influential than strain-field interactions.

Abstract

Temperature dependences of a magnetic and an orbital Bragg reflection at the Mn L2 and L3 edges of La0.5Sr1.5MnO4 have been collected. The temperature evolution of the orbital reflection depend strongly on the x-ray energy and reflects the different order parameteres for orbitals and Jahn-Teller distortions. The gradual increase of the orbital order parameter indicates that the orbital order and not the Jahn-Teller distortion drives the metal-insulator transition. Correspondingly, the orbital-orbital (super) exchange interaction dominates over the Jahn-Teller strain-field interaction.