Stabilization of charge and orbital ordered states by antiferromagnetism in the A-site ordered YBaMn2O6

TL;DR

This study uses Raman scattering to investigate how antiferromagnetic spin ordering stabilizes charge and orbital ordered states in YBaMn2O6 across a wide temperature range, revealing coexistence and phonon anomalies.

Contribution

It demonstrates that antiferromagnetic order stabilizes charge and orbital ordering in YBaMn2O6, with detailed phonon behavior analysis across temperatures.

Findings

Charge and orbital order coexist with metallic state down to T_N=195K.

Antiferromagnetic order induces zone-folded modes and phonon anomalies.

Spin ordering stabilizes the charge and orbital ordered states below T_N.

Abstract

We report on Raman scattering measurements of the A-site ordered YBaMn2O6 in the wide temperature range of 10-650K. Upon cooling almost all phonon modes show pronounced temperature dependencies of frequency, linewidth, and scattering intensity. This suggests that the octahedra tilting, Mn-O bond angles and lengths vary with temperature in a concerted way. The remarkable feature is that the high-temperature metallic and the charge and orbital ordered (CO-OO) states coexist down to T_N=195K. In the antiferromagnetic state zone-folded modes are induced by the CO-OO superstructure and the phonon modes undergo an anomalous softening and narrowing. Our results evidence that the CO-OO state is stabilized by the spin ordering for temperatures below T_N.