Mesoscopic thermodynamics of an inhomogeneous colossal-magnetoresistive phase

Equilibrium conductivity fluctuations of mesoscopic domains are found in fi lm and bulk single-crystal manganite colossal magnetoresistive material. Te mperature and field dependences of the Boltzmann factors for a collection o f two-state fluctuators give measures of the magnetic moment and entropy di fferences between the states, and of the fluctuator volumes. The large resi stance step size implies dramatic current inhomogeneities. Occasional anoma lous temperature dependences indicate that the film inhomogeneous phase is stabilized by a repulsive interaction between conducting regions.