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Correlation between thermoelectric properties and magnetic phases in the charge-ordered Pr0.5Sr0.5-xCaxMnO3

Abstract:

We have performed measurements of thermoelectric power (TEP), electrical resistivity, DC magnetization and X-ray powder diffraction in polycrystalline samples of the charge-ordered manganite Pr<inf>0.5</inf>Sr<inf>0.5-x</inf>Ca<inf>x</inf>MnO<inf>3</inf> for x = 0, 0.1 and 0.2. All the studied samples revealed three magnetic phases: paramagnetic at high temperatures, ferromagnetic below T<inf>C</inf> down to T<inf>N</inf>, below which the antiferromagnetic phase is established. At the paramagnetic-ferromagnetic transition, the TEP presents a clear break, and the three samples show metallic resistivity below T<inf>C</inf>. On the other hand, below T<inf>N</inf> all the samples turn to an insulating-like resistivity, but the TEP shows striking differences between the x = 0 sample and the other two. These differences are compatible with the different lattice and magnetic structures of the samples. These results support the idea that below T<inf>N</inf> a 2D-metal is present and no charge-order accompanies the A-type antiferromagnetic phase.