Metastable Resistivity States and Conductivity Fluctuations in Low-doped La$_{1-x}$Ca$_{x}$MnO$_3$ Manganite Single Crystals

TL;DR

This study investigates conductivity noise and resistivity states in low-doped LaCaMnO3 single crystals, revealing non-equilibrium 1/f noise behavior linked to inelastic tunneling and microcrack-induced energy landscape variations.

Contribution

It demonstrates the connection between metastable resistivity states, conductivity fluctuations, and inelastic tunneling mechanisms in manganite crystals.

Findings

Noise is of 1/f type across states.

High-temperature noise scales with bias squared.

Non-monotonic noise behavior at low temperatures.

Abstract

Conductivity noise in dc current biased La_{0.82}Ca_{0.18}MnO_{3} single crystals has been investigated in different metastable resistivity states enforced by applying voltage pulses to the sample at low temperatures. Noise measured in all investigated resistivity states is of 1/f-type and its intensity at high temperatures and low dc bias scales as a square of the bias. At liquid nitrogen temperatures for under bias exceeding a threshold value, the behavior of the noise deviates from above quasi- equilibrium modulation noise and depends in a non monotonic way on applied bias. The bias range of nonequilibrium 1/f noise coincides with the range at which the conductance increases linearly with bias voltage. This feature is attributed to a broad continuity of states enabling indirect inelastic tunneling across intrinsic tunnel junctions. The nonequilibrium noise has been ascribed to indirect intrinsic tunneling mechanism while resistivity changes in metastable states to variations in the energy landscape for charge carriers introduced by microcracks created by the pulse procedures employed