Universal relationship between magnetization and changes in the local structure of La1-xCaxMnO3:: Evidence for magnetic dimers -: art. no. 106401

We present extensive x-ray absorption fine structure measurements on La1-xCaxMnO3 as a function of the B field (to 11 T) and Ca concentration, x (21%-45%). These results reveal local structure changes (associated with polaron formation) that depend only on the magnetization for a given sample, irrespective of whether the magnetization is achieved through a decrease in temperature or an applied magnetic field. Furthermore, the relationship between local structure and magnetization depends on the hole doping. A model is proposed in which a filamentary magnetization initially develops via the aggregation of pairs of Mn atoms involving a hole and an electron site. These pairs have little distortion and it is likely that they form at temperature T-* above T-c.