Abstract
Magnetization curves along the c-axis of natural pyrrhotite crystal (Fe7S8) are measured in high magnetic field (up to about 100 kOe) from room temperature down to liquid helium temperature. By means of the X-ray method, it is also confirmed that the ordered arrangement of vacant sites and ions has no temperature dependence in the range from 80°K to 300K°. The magnetic results are well explained on the basis of Adachi’s theory that the magnetocrystalline anisotropy is caused by the ordered arrangement of vacant sites, and ferric and ferrous ions.