Very Unusual Magnetic Properties in Multi-walled Carbon Nanotube Mats

摘要

We report magnetic measurements up to 1100 K on a multi-walled carbonnanotube mat sample using a Quantum Design vibrating sample magnetometer. In anultra-low field (H = -0.02 Oe), we find a very large paramagneticsusceptibility (up to 12.7% of 1/4pi) at 1100 K and a very large diamagneticsusceptibility (at least 8.4% of -1/4pi) at 482 K. A small magnetic field (2.1Oe) completely suppresses the diamagnetic susceptibility at 482 K and reducesthe paramagnetic susceptibility at 1100 K by a factor of over 20. We rule outexplanations based on magnetic contaminants, instrument artifacts, and orbitaldiamagnetism. The magnetic data are inconsistent with any known physicalphenomena except for granular superconductivity. The present results suggestthe existence of an unknown new physical phenomenon or superconductivity withan ultra-high transition temperature.