Detecting the spinel–post-spinel transition in Fe₃O₄by<i>in situ</i>electrical resistivity measurements

Abstract

The phase transformation of magnetite to h-Fe3O4 was investigated at high pressure and temperature by in situ resistivity measurements in a multi-anvil press. Experiments at pressures≤9 GPa show similar resistivity paths during heating and cooling, indicating the stability of magnetite. During heating at 10 and 12 GPa, a distinctive jump in resistivity occurred that is attributed to the formation of h-Fe3O4. Microstructural investigations by TEM confirm this conclusion. Our results imply that the magnetite–h-Fe3O4 phase boundary is nearly isobaric and must lie between 9 and 10 GPa.