Anomalous temperature behavior of resistance in C1-xCox thin films grown by pulsed laser deposition technique

Journal of Alloys and Compounds Volume: 667 Pages: 18-22 Published: 2016

Typical FEG SEM image of deposited C1-xCox films

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Writers: S. Sergeenkov and C. Córdova and L. Cichetto Jr. and O.F. de Lima and E. Longo and F.M. Araújo-Moreira

Keywords: Carbon-cobalt nanocompositeThin filmsResistancePolaron hopping; Magnetic scattering

Abstract: We study the transport properties of C1−xCox thin films (with x = 0.1, 0.15 and 0.2) grown on Si substrate by pulsed laser deposition technique. The results demonstrate some anomalous effects in the behavior of the measured resistance R(T,x). More specifically, for 0 < T < T range (with T ≃ 220 K  ), the resistance is shown to be well fitted by a small polaron hopping scenario with View the MathML source and a characteristic temperature T0(x)≃T0(0)(1−x) (with T0(0) = 120 K). While for higher temperatures T < T < TC(x), the resistance is found to be linearly dependent on spontaneous magnetization M(T,x), viz. RM(T,x)∝M(T,x), following the pattern dictated by electron scattering on cobalt atoms formed robust ferromagnetic structure with the Curie temperature TC(x  ) obeying a percolation like law TC(x)≃TC(xm)(x/xm)0.15 with TC(xm) = 295 K   and the maximum zero-temperature magnetization reaching M(0,xm)≃0.5μB per Co atom for xm = 0.2.

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