Common features of nanoscale structural correlations in magnetoresistive manganites with a ferromagnetic low-temperature state

We report x-ray scattering studies of nanoscale structural correlations in Nd 1 - x Sr x MnO 3 and La 1 - x (Ca,Sr) x MnO 3 , x=0.2-0.5. We find that the correlated regions possess a temperature-independent correlation lengthof 2-3 lattice constants which is the same in all samples. The period of the lattice modulation of the correlated regions is proportional to the Ca/Sr doping concentration x. Remarkably, the lattice modulation periods of these and several other manganites with a ferromagnetic ground state fall on the same curve when plotted as a function of x. Thus, the structure of the correlated regions in these materials appears to be determined by a single parameter x. We argue that these observations provide important clues for understanding the colossal magnetoresistance phenomenon in manganites.