X-ray Scattering Studies of Correlated Polarons in La_(0.7)Ca_(0.3)MnO_3

摘要

We report x-ray scattering studies of diffuse peaks in the paramagnetic insulating phase of La_(0.7)Ca_(0.3)MnO_3. The peaks occur at a (0.5 0 0)/(0 0.5 0)-type wavevector, and are found to disappear abruptly upon cooling through the transition into the ferromagnetic metallic phase. Based on the wavevector and measured correlation length of 1-2 lattice constants, the peaks are found to be consistent with the formation of CE-type bipolarons, and their collapse at T_c is attributed to the energy gain associated with itineracy in the ferromagnetic state.