Hopping Transport and Spin-Polarized Tunneling Mechanism in Cr-Doped Gd0.7Ca0.3Mn1−x Cr x O3 (x = 0.0–0.5)

Hopping Transport and Spin-Polarized Tunneling Mechanism in Cr-Doped Gd0.7Ca0.3Mn1−x Cr x O3 (x... Temperature-dependent DC electrical resistivity of polycrystalline samples with orthorhombic perovskite structure Gd0.7Ca0.3Mn1−x Cr x O3 (x = 0.0–0.5) has been reported. The samples were prepared by the solid-state reaction method. The resistivity of all the samples indicates a semiconducting nature. In the high-temperature region, the electrical conduction process follows the small polaron hopping (SPH) mechanism showing exponential variation of resistivity with temperature. The activation energy increases with Cr concentration. The low-temperature resistivity data follows Mott’s ln(ρT −1/2)∼T −1/4 law of variable-range hopping (VRH) conduction mechanism. The estimated values of hopping distances (R) and hopping energies (W) of the samples start to increase with increasing Cr concentrations from and above x = 0.5 and satisfy essential conditions of the Mott VRH, i.e., αR>> 1 (α = inverse localization length) and W/ K B T>> 1. This signifies that evaluation of these parameters being logical and the effect can be attributed to high density of doping which introduces simultaneously potential disorder and localized states. The magnetic field-dependent magnetoresistance has been explained by a phenomenological model considering spin-polarized tunneling at grain boundaries in the samples. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Superconductivity and Novel Magnetism Springer Journals

Hopping Transport and Spin-Polarized Tunneling Mechanism in Cr-Doped Gd0.7Ca0.3Mn1−x Cr x O3 (x = 0.0–0.5)

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Publisher
Springer US
Copyright
Copyright © 2017 by Springer Science+Business Media New York
Subject
Physics; Strongly Correlated Systems, Superconductivity; Magnetism, Magnetic Materials; Condensed Matter Physics; Characterization and Evaluation of Materials
ISSN
1557-1939
eISSN
1557-1947
D.O.I.
10.1007/s10948-017-4023-7
Publisher site
See Article on Publisher Site

Abstract

Temperature-dependent DC electrical resistivity of polycrystalline samples with orthorhombic perovskite structure Gd0.7Ca0.3Mn1−x Cr x O3 (x = 0.0–0.5) has been reported. The samples were prepared by the solid-state reaction method. The resistivity of all the samples indicates a semiconducting nature. In the high-temperature region, the electrical conduction process follows the small polaron hopping (SPH) mechanism showing exponential variation of resistivity with temperature. The activation energy increases with Cr concentration. The low-temperature resistivity data follows Mott’s ln(ρT −1/2)∼T −1/4 law of variable-range hopping (VRH) conduction mechanism. The estimated values of hopping distances (R) and hopping energies (W) of the samples start to increase with increasing Cr concentrations from and above x = 0.5 and satisfy essential conditions of the Mott VRH, i.e., αR>> 1 (α = inverse localization length) and W/ K B T>> 1. This signifies that evaluation of these parameters being logical and the effect can be attributed to high density of doping which introduces simultaneously potential disorder and localized states. The magnetic field-dependent magnetoresistance has been explained by a phenomenological model considering spin-polarized tunneling at grain boundaries in the samples.

Journal

Journal of Superconductivity and Novel MagnetismSpringer Journals

Published: Mar 16, 2017

References

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