Evidence of the Bi3+ lone-pair effect on the charge-ordering state: Resistivity and thermoelectric power of Bi0.5-yLa ySr0.5MnO3 (0.0≤y≤0.4)

Polycrystalline samples of Bi_0.5-yLa_ySr _0.5MnO₃ (0.0≤y≤0.4) (BLSMO) have been synthesized to investigate the Bi³⁺ lone-pair effect on the long-range charge-ordering (CO) state. Since the ionic size of La³⁺ is similar to that of Bi³⁺ 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-xSr_xMnO₃ (BSMO). Finally, we found that the Bi³⁺ lone pairs play an important role in the anomalously high T_CO in BSMO. © IOP Publishing Ltd.