Temperature Variation of the Abnormal Unidirectional Diamagnetism of Graphite Crystals

Abstract

As is well-known, graphite crystal exhibits some remarkable magnetic properties. The susceptibility along the hexagonal axis of the crystalχ_¶, is about 22 × 10⁻⁶ per gm., at room temperature, while that along directions in the basal plane, χ_¶ is 0.5 × 10⁻⁶ only¹—the latter value being nearly the same as that of diamond. The abnormal diamagnetism of graphite is thus more or less confined to one direction. Further, this abnormal diamagnetism is very sensitive to any chemical treatment of the crystal. For example, on treating the crystal with a mixture of strong nitric and sulphuric acids, when it swells up to blue graphite, diminishes numerically from 22 × 10⁻⁶ to less than 2 × 10⁻⁶, whereas χ_¶. remains practically unchanged. Also an indefinite diminution in the size of the crystal appears to have the same effect.