The atomic structure is an important component in the mechanism of the colossal magnetoresistance (CMR) phenomenon mainly through the ionic size effect. In the current understanding, this factor controls the CMR phenomenon by changing the electron bandwidth, while the estimated changes in the bandwidth appear to be too small to be of significance. By way of the atomic pair distribution function analysis of pulsed neutron diffraction data of model compounds, we suggest that the principal effect of the ionic size is to change the polaron formation energy through the change in the local elastic response.

• Received 28 June 2001

DOI:https://doi.org/10.1103/PhysRevB.64.180403