Structural, electrical, magnetic and thermal studies on Eu_1-xSr_xMnO₃ (0.2 ≤ x ≤ 0.5) manganites

In the present work, a series of Eu_1-xSr_xMnO₃ (0.2 ≤ x ≤ 0.5) manganites has been prepared and systematic investigation on structural, electrical, magnetic and thermoelectric properties is reported. The samples were prepared by conventional solid-state reaction. The samples are crystallized in orthorhombic crystal structure with Pbnm space group. Rietveld analysis of XRD results show the unit volume is decreasing with increasing Sr content. The observed grain size is decreasing with increase the concentration of Sr. All the samples are found to exhibit insulating behaviour down to the low temperatures. The magnetization results reveal that the antiferromagnetic (AFM) nature is observed in zero field condition (ZFC), while ferromagnetic (FM) behaviour is observed under field cooled conditions (FC). The samples with x = 0.2 and 0.3 show the spin glass behaviour in ZFC condition. The metamagnetic behaviour is observed at low temperatures for the samples with x = 0.4 and 0.5. The thermoelectric power (S) of the samples with x = 0.4 & 0.5 is negative at high temperature range. The samples with x = 0.4 exhibits a crossover in S from positive to negative values. Samples with x = 0.3 and 0.2 show positive S value for entire temperature range. The analysis of S value indicates the small polaron hopping model is presence in the high temperature region.