Impact of Charge Ordering on Magnetic Correlations in Perovskite (Bi,Ca)MnO_3

TL;DR

This study investigates how charge ordering influences magnetic correlations in (Bi,Ca)MnO3, revealing a transition from ferromagnetic to antiferromagnetic spin fluctuations associated with structural changes.

Contribution

It demonstrates the impact of charge ordering on magnetic interactions and the role of Jahn-Teller electrons in these insulating perovskites, providing new insights into their magnetic behavior.

Findings

Dynamic ferromagnetic correlations at high temperatures

Transition to antiferromagnetic fluctuations during charge ordering

Charge ordering competes with double-exchange ferromagnetism

Abstract

Single crystalline (Bi,Ca)MnO3 (74< %Ca <82) were studied with neutron scattering, electron diffraction and bulk magnetic measurement. We discovered dynamic ferromagnetic spin correlations at high temperatures, which are replaced by antiferromagnetic spin fluctuations at a concomitant charge ordering and structural transition. Our results indicate that thermal-activated hopping of the Jahn-Teller active e_g electrons in these insulating materials, nevertheless, induce ferromagnetic interaction through double-exchange mechanism. It is the ordering of these charges competing with the double-exchange ferromagnetic metallic state.