MAGNETIC PROPERTIES, MECHANISMS OF ELECTRICAL CONDUCTIVITY AND MAGNETORESISTANCE IN La0.5Sr0.5Mn1−yFeyO3 AT 0 ≤ y ≤ 0.1
DOI:
https://doi.org/10.52575/2687-0959-2020-52-4-271-285Keywords:
hopping conductivity, Jahn - Teller effect, ceramics, magnetic field, temperature dependenceAbstract
We investigated the influence of Fe doping on the magnetic properties, mechanisms of electrical conductivity and magnetoresistance of polycrystalline La0.5Sr0.5MnO3, which is in a state of phase separation. The results show that at a Fe concentration ≤ 5%, in the entire temperature range under study, the long-range order of the charge-ordered (CO) state is weakened. This leads to the fact that short-range CO clusters are embedded in a ferromagnetic (FM) metal matrix, with the electrical resistance indices decreasing to the phase of a homogeneous metal. However, further doping with Fe leads to the opposite tendencies, which is explained by the effect of weakening the double exchange, which is dominant at Fe concentrations > 5%. The temperature dependence of the resistivity in the region of the CO phase obeys the mechanism of hopping conductivity with a variable hopping length of the Shklovsky - Efros type. This behavior is determined by the appearance of a soft Coulomb gap ∆ ≈ 0.32 eV in the density of localized states and a hard gap δv, which was calculated and discussed. An analysis of the field dependence of the resistivity at fixed temperatures indicated the presence of the colossal magnetoresistance (CMR) effect in the sample with a Fe concentration of ≈ 10%, and a possible explanation was given.Downloads
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