Magnetism, transport and charge order in Bi1-xSrxMnO3

The structural, magnetic and transport properties in the strontium rich part of Bi1-xSrxMnO3 solid solution (x is contained in <0.5;1>) were examined by X-ray powder diffraction, DC susceptibility, thermopower, resisitivity and thermal conductivity measurements. All material characteristics are significantly changed at the temperature of charge ordering, TCO, which gradually decreases from ∼550 K for x=0.5 to almost 0 K at x=0.9. Above TCO a temperature independent thermopower, whose absolute value increases with x, indicates polaronic transport. Below TCO an activated transport mechanism of localized charge carriers is observed. The Weiss temperature decreases with x and becomes negative for x=0.8 suggesting antiferromagnetic interactions at high temperatures. The evolution of the above-mentioned effects is accompanied by a progressive decrease of orthorhombic distortion at room temperature