Noise signatures of metastable resistivity states in ferromagnetic insulating manganite

Abstract

Pronounced noise signatures enabling one to discriminate metastable resistivity states in La0.86Ca0.14MnO3 single crystals have been observed. The normalized noise spectra for metastable resisitivity differ both in shape and magnitude, indicating that the metastable state is associated with transition of the electronic system into another local minimum of the potential landscape. Such scenario is consistent with freezing of the electronic system into a Coulomb glass state.

Meyer-Neldel rule in the conductivity of phase separated manganites

“…Obviously, this conclusion does not violate the II thermodynamics law because the investigated system is not an insulated one. On the other hand, the conclusion of the progressive ordering of the metastable state concurs with results of our independent noise investigations of the metastable resistivity states [9].…”

“…As fabricated La 0.86 Ca 0.14 MnO 3 crystals was found to be in the high resistivity state. However, already during the very first thermal cycles between liquid He and room temperatures, accompanied by bias current sweeps, the pristine HRS spontaneously evolved into the low resistivity metastable state, as discussed in details elsewhere [9,13]. The LRS was characterized by a long lifetime and persisted for more than three months of continuous experimentation.…”

“…The unusual consequences of phase separation in manganites include the colossal magnetoresistive effect (CMR) and appearance of peculiar long and short life-time metastable states with different resistivity. The metastable states appear either spontaneously, or became induced by changing external parameters such as temperature, magnetic field or electrical bias [5][6][7][8][9]. The nature of physical mechanisms responsible for this metastability are still not fully understood.…”

Noise Features of Metastable Resistivity States in La0.86Ca0.14MnO3 Manganite Single Crystal

“…We have studied electronic transport and noise in freshly synthesized La 0:86 Ca 0:14 MnO 3 single crystals in their pristine high-resistivity state (HRS) and in spontaneously created low-resistivity state (LRS). For more details on crystal evolution between metastable resistivity states, see [2]. The power spectral density (PSD) of the conductivity noise in pristine HRS has almost exclusively 1=f-like character.…”

“…The level of the normalized 1=f voltage noise in the LRS is markedly higher than in the HRS. The detailed understanding of the noise¯ngerprints [2] and life spans of metastable resistivity states remains as one of the unsolved problems of noise in the discussed system.…”