Double-percolation and magnetoresistance effects in ferromagnet-superconductor nanoparticle composites
We investigate transport and magnetotransport properties of binary networks composed of superconducting (MgB2) and ferromagnetic (CrO2 or LSMO) nanoparticles. While for the LSMO/MgB2 system a single percolation threshold is observed, for CrO2/MgB2 binary composites an anomalously high resistance sta...
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Main Authors | , , , , |
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Format | Journal Article |
Language | English |
Published |
14.06.2011
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Subjects | |
Online Access | Get full text |
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Summary: | We investigate transport and magnetotransport properties of binary networks
composed of superconducting (MgB2) and ferromagnetic (CrO2 or LSMO)
nanoparticles. While for the LSMO/MgB2 system a single percolation threshold is
observed, for CrO2/MgB2 binary composites an anomalously high resistance state
with two distinct percolation thresholds corresponding to conductor-insulator
and superconductor-insulator transitions is found. The existence of this double
percolation effect becomes possible when the interface conductance between the
two different constituents is suppressed and the condition for the two
thresholds PI + PII > 1 is satisfied. For MgB2 an unusually large value of the
threshold is observed, which can be explained by the significant geometric
disparity between nanoparticles of the two constituents, resulting in a large
excluded volume for MgB2 nanoparticles. The scaling behavior near both
thresholds is determined, with the two critical exponents identified: \mu
\approx 2.16 \pm 0.15 for the insulating-conducting transition on the CrO2 side
and s = 1.37\pm 0.05 for the insulating - superconducting transition on the
MgB2 side. We also measure the magnetoresistance for the entire series of
CrO2/MgB2 samples, with a maximum of approximately 45% observed near the
percolation threshold at liquid He temperatures. |
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DOI: | 10.48550/arxiv.1106.2862 |