Electron transport and thermoelectric properties of layered perovskite LaBaCo2O5.5

TL;DR

This study explores the electrical, magnetic, and thermoelectric properties of LaBaCo2O5.5, revealing complex conduction mechanisms, phase transitions, and significant thermopower behavior linked to polaronic conductivity and magnetic interactions.

Contribution

It provides a comprehensive analysis of transport properties in LaBaCo2O5.5 using various models, highlighting unique thermoelectric and magnetoresistance behaviors near phase boundaries.

Findings

Semiconductor-semiconductor transition at 326K linked to ferromagnetic transition

Resistivity follows variable range hopping at low temperatures

Maximum thermopower of 303 μV/K at 120K

Abstract

We have investigated the systematic transport properties of the layered 112-type cobaltite LaBaCo2O5.5 by means of electrical resistivity, magnetoresistance, electroresistance and thermoelectric measurements in various conditions. In order to understand the complex conduction mechanism of LaBaCo2O5.5, the transport data have been analyzed using different theoretical models. The system shows semiconductor-semiconductor like transition (TSC) around 326K, corresponding to ferromagnetic transition and in the low temperature region resistivity data follows the Motts variable range hopping model. Interestingly, near and below the room temperature this compound depicts significant change in electro- and magnetoresistance behavior, the latter one is noteworthy near the magnetic phase boundary. The temperature dependence of thermopower, S(T), exhibits p-type polaronic conductivity in the temperature range of 60-320K and reaches a maximum value of 303 uV/K (at 120K). In the low temperature AFM region, the unusual S(T) behavior, generally observed for the cobaltite series LnBaCo2O5.5 (Ln = Rare Earth), is explained by the electron magnon scattering mechanism as previously described for perovskite manganites.