High frequency cut-off in 1/f conductivity noise of hole-doped La1−x Ca x MnO3 manganite single crystals

High frequency bias and temperature-dependent Lorentzian cut-off has been observed in the 1/f spectra of the conductivity fluctuations in low hole-doped ferromagnetic insulating La1-xCaxMnO3 manganite at low temperatures. The cut-off frequency depends on dc current bias and temperature. The high frequency cut-off has been tentatively associated with intrinsic limits of the appearance of 1/f noise in the hopping regime of the Coulomb glass state. The assumption is validated by the fact that the Efros-Shklovskii temperature T-ES, estimated from the fit of the model to the experimentally measured temperature dependence of the cut-off frequency, has the same value as the temperature T-ES evaluated independently from the temperature dependence of the resistivity in the corresponding temperature range.