We report the observation of a giant positive magnetoresistance in millimetre scale hydrogenated graphene with magnetic field oriented in the plane of the graphene sheet. A positive magnetoresistance in excess of 200% at a temperature of 300 mK was observed in this configuration, reverting to negative magnetoresistance with the magnetic field oriented normal to the graphene plane. We attribute the observed positive, in-plane, magnetoresistance to Pauli-blockade of hopping conduction induced by spin polarization. Our work shows that spin polarization in concert with electron-electron interaction can play a dominant role in magnetotransport within an atomic monolayer.
The problems of elaboration and application of microand nanometer sized antennas for the generation and reception of electromagnetic radiation is still relevant in both fundamental and applied aspects. With decreasing antenna size, the frequency of electromagnetic radiation increases, and its power decreases. To increase the radiation power, the periodic (in space) electrodynamic structures are used. The aim of the work is to find the possibility of application of injection and (quasi)ballistic drift of single electrons inside curved carbon nanotubes for emission of electromagnetic waves in the microwave range and to determine the parameters of the radiating system that affect the radiation power.By the calculation within the framework of classical electrodynamics it is shown the possibility in principle of generation of electromagnetic radiation of the gigahertz range by a stream of single electrons inside a hollow curved dielectric carbon nanotube.It was found that the spectrum and power of this radiation can be controlled by varying the electron flux density, length and curvature of the hollow nanotube.The results of the work can be applied for elaboration of a microminiature emitter of microwave electromagnetic radiation based on a curved carbon nanotube in the engineering of contactless probe microscopy.
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