Equilibrium conductivity fluctuations of mesoscopic domains are found in film and bulk single-crystal manganite colossal magnetoresistive material. Temperature and field dependences of the Boltzmann factors for a collection of two-state fluctuators give measures of the magnetic moment and entropy differences between the states, and of the fluctuator volumes. The large resistance step size implies dramatic current inhomogeneities. Occasional anomalous temperature dependences indicate that the film inhomogeneous phase is stabilized by a repulsive interaction between conducting regions.

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Epitaxial films of La 0.72 Sr 0.28 MnO 3 ͑LSMO͒ are found to show almost no excess conductivity fluctuations associated with the colossal-magnetoresistive transition, in contrast to the closely related material La 0.67 Ca 0.33 MnO 3 ͑LCMO͒. The result fits with the contrast between the suspected second-order transition in LSMO and the ͑locally͒ first-order transition and mixed phase in LCMO.

Barkhausen noise, measured at four different sweep rates, is used to reconstruct and study the effective pinning field present in an amorphous metallic ferromagnet. This reconstruction technique gives pinning field spatial spectra similar to those measured previously. However, the pinning field is not reproducible from sweep to sweep and has statistical properties which depend systematically on the sweep rate, confirming that it is a collective effect of the dynamics of flexible domain walls. The statistics were non-Gaussian, requiring some modification of theories of effective pinning potentials.

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