Abstract
A quantitative determination of the statistical distribution of the Mn–O instantaneous bond lengths in the La
0.75Ca
0.25MnO
3 system by Mn K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy shows that the giant magneto-resistance (GMR) transition occurs at a crossover from a metallic phase with large (or intermediate) polarons to an insulating phase where small polarons coexist with large (or intermediate) polarons. In the GMR region, the two Mn polaronic domains coexist and share half of the space.