Non-Gaussian resistance noise in the ferromagnetic insulating state of a hole-doped manganite

Abstract

We report the observation of a large 1/f noise in the ferromagnetic insulating state (FMI) of a hole doped manganite single crystal of La0.80Ca0.20MnO3,which manifests hopping conductivity in the presence of a Coulomb gap. The temperature-dependent noise magnitude decreases in the FMI state indicating a sharp freeze-out of the noise magnitude with temperature on cooling. As the material is cooled down below the ferromagnetic transition TC, the noise becomes non-Gaussian, as seen through the probability density function and second spectra. On further cooling in the FMI state, the noise becomes more non-Gaussian. The non-Gaussian noise is proposed to arise from charge fluctuations in a correlated glassy phase of the polaronic carriers which develop in these systems, as reported in recent simulation studies.