Glass transition in the polaron dynamics of colossal magnetoresistive manganites

Neutron scattering measurements on a bilayer manganite near optimal doping show that the short-range polaron correlations are completely dynamic at high T , but then freeze upon cooling to a temperature T*approximate to310 K . This glass transition suggests that the paramagnetic/insulating state arises from an inherent orbital frustration that inhibits the formation of a long-range orbital- and charge-ordered state. Upon further cooling into the ferromagnetic-metallic state (T-C=114 K) , where the polarons melt, the diffuse scattering quickly develops into a propagating, transverse optic phonon.