Persistent currents and magnetic flux trapping in fragments of carbon deposits containing multiwalled nanotubes

It is found that the magnetization curves of samples of fragments of cathode carbon deposits with a high content of multiwalled nanotubes exhibit a pronounced irreversible character, attesting to the induction of persistent currents in the samples and to magnetic flux trapping, as happens in a multiply connected superconducting structure. A decrease of the trapped flux in time could not be observed at low (helium) temperatures with a measurement time of about 20 h. For intermediate (~30K) and room temperatures the trapped magnetic flux decays slowly with characteristic relaxation times of the order of 150 and 15 h, respectively.