Negative magnetoresistance in glassy carbon

Abstract

An extensive experimental investigation of the negative magnetoresistance phenomenon in a non-crystalline carbon has been carried out. The microstructure of the material was altered by heat treating in the range 1000°−2800°C, and the effect of the changes induced was measured as a function of temperature (10–300 K) and magnetic field (0–50 kG). The negative magnetoresistance was found to follow a f(H/T ^1/2) dependence over a large range of temperatures and magnetic fields. The mechanism is thought to be spin-flip scattering from localized spins. Starting with Δρ∞ −m ², where m is the magnetic moment per localized spin, the discussion relates the observed negative magnetoresistance to the anomalous behaviour of the spin susceptibility on the metallic side of the metal-insulator transition.