Charge melting and polaron collapse in La1.2Sr1.8Mn2O7

X-ray and neutron scattering measurements directly demonstrate the existenc e of polarons in the paramagnetic phase of optimally doped colossal magneto resistive oxides. The polarons exhibit short-range correlations that grow w ith decreasing temperature, but disappear abruptly at the ferromagnetic tra nsition because of the sudden charge delocalization. The "melting" of the c harge ordering as we cool through T-C occurs with the collapse of the quasi static polaron scattering, and provides important new insights into the rel ation of polarons to colossal magnetoresistance.