Transport-entropy correlations in La0.7Ca0.3MnO3 manganite

An investigation of the magnetic entropy change ΔSM and resistivity ρ, and the relation between them, for La0.7Ca0.3MnO3 (LCMO) material has been presented. By using an equation of the form ΔSM=−α∫0H[δln(ρ)δT]HdH (α=9.98 emu/g), which relates magnetic order to transport behavior of the compounds, we measure the magnetic entropy change ΔSM from the resistivity measurement, where the resistivity results agree quite well with the fitting parameter α=9.98 emu/g in the intermediate temperature range. This result reveals the predominant role of magnetic polarons on the magnetoresistive property of manganites. It is obvious that magnetic disorder, characterized by ΔSM, affects the magnetic polarons, while the magnetic polarons influence the electronic transport properties, which may be the underlying reason for a salient ΔSM−ρ relation. It also provides an alternative method to determine magnetic entropy change on the basis of resistive measurements.