HALL-EFFECT STUDIES ON PYRRHOTITE

Measurements on natural crystals of pyrrhotite from room temperature to beyond the Neel point are reported. This material is known as a ferrimagnetic semiconductor, and also for its magnetic anisotropy. The isotherms of the Hall effect are given for samples cut in such a way that the magnetic field is applied along the c axis and perpendicular to it. The sign of the ordinary Hall effect proves that, in the measured temperature region, the conductivity is of p type. The energy gap can be derived from the ordinary Hall effect, and is ten times smaller along the c axis than in a direction perpendicular to it. The spontaneous coefficient R//s falls with increasing temperature, as happens in other antiferromagnetic and ferrimagnetic materials.