SELF-REVERSAL OF ISOTHERMAL REMANENT MAGNETIZATION IN A PYRRHOTITE (FE7S8) CRYSTAL

The remanent magnetization induced at room temperature (IRM) was measured for powder and massive specimens separated from a Fe7S8 Crystal. To characterize the crystal, several methods were used including Mossbauer spectroscopy, thermomagnetic analysis, low-field susceptibility anisotropy and magnetic colloid method. Self-reversals of IRM were revealed in the massive crystal fragment after its magnetization in magnetic fields of the order of 10-10(2) mT. Both normal and reverse IRM vectors lay in the maximum susceptibility plane perpendicular to the crystallographic c'-axis of the crystal. A twinning also perpendicular to the crystal's c'-axis and a very low coercivity in each twin (monocrystallic layer) probably support the origin of the reverse IRM in the crystal.