Very Unusual Magnetic Properties in Multi-walled Carbon Nanotube Mats

TL;DR

This study reports unprecedented magnetic behaviors in multi-walled carbon nanotube mats at high temperatures, suggesting possible new physical phenomena or ultra-high temperature superconductivity.

Contribution

It presents novel magnetic measurements indicating potential superconductivity or unknown phenomena in carbon nanotube mats at very high temperatures.

Findings

Large paramagnetic susceptibility at 1100 K

Large diamagnetic susceptibility at 482 K

Suppression of magnetic responses by small magnetic fields

Abstract

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