Dresden 2014 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 18: Carbon: Diamond, nanotubes and Buckyballs
HL 18.5: Talk
Monday, March 31, 2014, 16:00–16:15, POT 112
Unusual Hysteresis Observed in the Magnetoresistance of Multiwall Carbon Nanotubes Bundles — •Jose Barzola-Quiquia1, Manuel Lindel1, M. Muallem2, Gilbert D. Nessim2, and Pablo Esquinazi1 — 1Division of Superconductivity and Magnetism, Institute for Experimental Physics II, University of Leipzig, D-04103 Leipzig, Germany — 2Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel
The magnetotransport properties of several hundreds of micrometer long multi-walled carbon nanotubes (MWCNT) bundles were studied. The samples were contacted with silver paste and showed ohmic behavior at temperatures above 10 K, i.e. linear current-voltage (I-V) curves. The temperature dependence of the resistance is well described by variable-range hopping mechanism for one-dimensional systems. In this temperature range the magnetoresistance is negative and can be explained using an empirical model based on spin-scattering processes that suggests the existence of magnetic order. No magnetic impurities were found by means of energy dispersive X-ray. At temperatures between 2 K and 12 K, the I-V curves showed a nonlinear behavior, indicating the existence of a potential barrier. In this temperature range and at low magnetic fields and low enough input currents the magnetoresistance changed to positive accompanied by a clear hysteresis. The hysteresis as well as the positive magnetoresistance vanished at large inputs currents. Our results indicate that at T < 12 K the unusual butterfly hysteresis in the magnetoresistance is directly related to the nonlinear I-V behavior and suggests superconducting.