Electric and Magnetic Properties of Cubanite

The electric and magnetic properties of natural and synthetic cubanite were investigated. The electric conductivity of natural cubanite increases with increasing temperature and shows an anomalous change at 245°C, where transformation from the low temperature orthorhombic form to the high temperature cubic one is assumed to appear, and the mineral behaves as a typical semiconductor in the low temperature range but as a metallic conductor above the polymorphic transition temperature. The conductivity of synthetic cubanite is metallic in the whole temperature range measured.
Cubanite in natural orthorhombic form is weakly ferromagnetic (e.g., 1.40 emu/gr, equivalent to 0.34 μB,/mol, at 25°C) but behaves paramagnetically above the transition temperature. No matter whether it may be synthetic or derived from the natural orthorhombic form, the cubic cubanite shows no anomaly in magnetic susceptibility at 245°C on cooling but increases its value abruptly just at the liquid nitrogen temperature and displays a ferrimagnetic property. Natural cubanite is easily magnetizable along the b-axis.
This is the first report of the ferrimagnetic character of a compound within the Cu—Fe—S system that was observed at the low temperature, and the origin of the ferromagnetism is discussed in relation to the crystal structure.