Peculiarities of Superconductive Phase in Nanographite Films

Report describes some unconventional electromagnetics properties of nanographite (NG) films which resemble room temperature superconductivity. NG film is the composite of 20–30 Å graphite clusters embedded in amorphous matrix. At such a small dimension, the superconductivity can be explained by the attraction of all electrons to all kernels of atoms constituting the graphite cluster. Possibilities of room temperature weak superconductivity in nanographite films are supported by the observation of reversed Josephson Effect (which is the transformation of microwave irradiation falling on the sample into the direct current through this sample) and its temperature dependence. This dependency is fully reminiscent of the behavior of known superconductors. Another effect is switching conductivity from high to very small value at some critical current (which can be used in electrical switchers), pinning of vortices on columnar topological structure of film observed in magnetic force microscope. In the article, an attempt is made to explain the appearance of coherent optical radiation upon conductivity switching in nanographite films by the movement of magnetic vortices and the thermomagnetic instability of their magnetic structure. Under the effort to find the state of global phase coherence in the nanographite films, the Josephson current at room temperature was detected, to the best of our knowledge, for the first time, when measuring the current–voltage characteristics.