Thermal and electronic transport properties and two-phase mixtures in La5/8-xPrxCa3/8MnO3

We measured thermal conductivity kappa, thermoelectric power S, ana electric conductivity a of La5/8-xPrxCa3/8MnO3, showing an intricate interplay between metallic ferromagnetism (FM) and charge ordering (CO) instability. The change of kappa, S, and sigma with temperature (T) and x agrees well with the effective medium theories for binary metal-insulator mixtures. This agreement clearly demonstrates that with the variation of T as well as x, the relative volumes of FM and CO phases drastically change and percolative metal-insulator transition occurs in the mixture of FM and CO domains.