Low-temperature carrier transport in magnetic field in sandwich-like graphene/Co nanoparticles/graphene structure

The improved analysis of carrier transport in the single-layer graphene and hybrid structures like graphene/Co nanoparticles (NPs) and graphene/Co NPs/graphene has been conducted. The temperature and magnetic field dependences of the sheet resistance R-Sq (T, B) and/or conductivity sigma(Sq) (T, B) has shown the coexistence of negative (NMR) and positive (PMR) contributions in magnetoresistive effect in all the samples under study. The dependences of R-Sq (T, B) and/or sigma(Sq) (T, B) were analyzed in the framework of some combinations of 5 models relating to quantum corrections (QCs) to Drude conductivity theory and different hopping models for variable range hopping (VRH) regimes. It was shown, in particular, that in the region of NMR effect below 75 K and in fields B < (0.5-1) T, sigma(Sq) (T, B) dependences obey the combination of QCs theory (at induction <100 mT) and conduction by coherent hopping over localized states in the VRH regime at T < 20 K. In this case, with the phase breaking time of the wave function it follows the power-like law tau(phi)(T) similar to T-p with the exponent p approximate to 1. These dependences also allowed to estimate the values of electron concentration n(T) in the structures studied, which were close to the values in the undoped graphene near the neutrality point. In the region of the PMR effect, the electrical resistance of the structures studied increases linearly with increasing B without saturation. This behavior is often attributed to the presence of structural inhomogeneities in the samples (due to e.g. Co-based nanoparticles) under study, which leads to distortion of the current paths under the action of the Lorentz force arising in a perpendicular magnetic field.

Automated summary

The study conducted an improved analysis of carrier transport in single-layer graphene and hybrid structures, showing the coexistence of negative and positive contributions in magnetoresistive effect. Various models were used to analyze the dependences on temperature and magnetic field, providing insights into the behavior of electrical resistance in the structures.