Noise probe explores the glassiness of Ferromagnetic Insulating (FMI) state in manganites

Abstract

The ferromagnetic insulating (FMI) state of low hole doped manganites forms a disordered electronic system showing Efros-Shklovskii variable range hopping (ESVRH) type hoping at low temperature with evidence of a soft Coulomb gap of ΔCG. The temperature dependent noise identified a freezing temperature where the freezing process is kinetically governed with the time scale determined by an activation energy similar to ΔCG. The activation barrier determined from noise matches closely with ΔCG obtained from transport measurement. At low temperatures the fluctuation develops a non-Gaussian component. Using higher order statistics of fluctuations we experimentally address the evidence of slowly driven kinetics and correlated motion of charge carriers in FMI states.