Evidence for non-adiabatic, small-polaron-mediated transport both above and below the ferromagnetic ordering temperature in O-depleted La0.67Ca0.33MnO3-δ

The transport and magnetic behaviours of Ar-annealed (O-depleted) bulk samples of an archetypal, 'optimally' doped manganese perovskite, La0.67Ca0.33MnO3, are reported, analysed and compared with those of an untreated specimen. These indicate that the transport data for both the paramagnetic and ferromagnetic phases of the O-depleted system are consistent with the predictions based on polaronic hopping, specifically non-adiabatic small-polaron hopping ton the basis of the internal consistency of estimates for the characteristic frequency Omega (0) from both the adiabatic and non-adiabatic formalisms). These results yield indirect support for models which attribute transport in doped perovskites in general, and the colossal-magnetoresistance phenomenon in particular, to polaronic behaviour.