Ordering phenomena and transport properties of Bi1/2Sr1/2MnO3 single crystals

TL;DR

This study investigates the ordering phenomena and transport properties of Bi1/2Sr1/2MnO3 single crystals, revealing charge ordering, low thermal conductivity, and phonon scattering mechanisms linked to Zener pairs and lattice displacements.

Contribution

It provides detailed insights into the charge order formation, structural transitions, and phonon scattering mechanisms in Bi1/2Sr1/2MnO3, combining transport measurements with diffraction data.

Findings

Charge order onset at 450 K with hysteresis below 535 K

Extremely low thermal conductivity unaffected by magnetic ordering

Charge ordered state involves Mn4+ dimers stabilized by lattice displacements

Abstract

Measurements of the electrical and thermal conductivities, thermopower and paramagnetic susceptibility have been performed on single crystal samples of Bi1/2Sr1/2MnO3 and complemented with the X-ray powder diffraction data. A pronounced hysteretic behavior, observed below the cubic-to- orthorhombic transition at Tcrit = 535 K, is related to the onset of long-range charge order at TCO = 450 K and its further evolution down to about 330 K. The diffraction data suggest that the charge ordered state is formed by Zener pairs, represented by Mn4+ dimers linked by one extra eg electron, and is possibly stabilized by cooperative Bi,Sr displacements. An extremely low thermal conductivity is observed down to the lowest temperatures, without any recovery at the anti- ferromagnetic ordering temperature TN = 150 K. Such be- havior points to a presence of strong scatterers of phonons. Their possible origin can be linked to "optical-like" oscilla- tions which are associated with fluctuating charges within the Zener pairs.