Evidence of the Bi(3+) lone-pair effect on the charge-ordering state: resistivity and thermoelectric power of Bi(0.5-y)La(y)Sr(0.5)MnO(3) (0.0≤y≤0.4).

Polycrystalline samples of Bi(0.5-y)La(y)Sr(0.5)MnO(3) (0.0≤y≤0.4) (BLSMO) have been synthesized to investigate the Bi(3+) lone-pair effect on the long-range charge-ordering (CO) state. Since the ionic size of La(3+) is similar to that of Bi(3+) and the Mn valence state does not change with La doping, we obtained the Bi lone-pair effect on the CO state without disturbance by other effects. The resistivity ρ(T) and thermoelectric power S(T) of BLSMO have been measured. A hysteretic behaviour was observed in both ρ(T) and S(T) for y = 0.1 and 0.2. From the onset of the hysteretic behaviour, we defined a charge-ordering temperature (T(CO)) and compared it to that of Bi(1-x)Sr(x)MnO(3) (BSMO). Finally, we found that the Bi(3+) lone pairs play an important role in the anomalously high T(CO) in BSMO.