Pressure-induced coordination crossover in magnetite, a high pressure Mössbauer study Original Research Article

Temperature-dependent 57Fe Mössbauer spectroscopy to 40 GPa shows that Fe3O4 magnetite undergoes a coordination crossover (CC) whereby charge-density is shifted from octahedral to tetrahedral sites and the spinel structure thus changes from inverse to normal with increasing pressure and decreasing temperature. A precursor to the CC is a d-charge decoupling within the octahedral sites at the inverse spinel phase. The CC-transition takes place almost exactly at the Verwey transition temperature (TV=122 K) at ambient pressure. While TV decreases with pressure, the CC-transition temperature increases with pressure, reaching 350 K at 10 GPa. The d electron localization mechanism proposed by Verwey and later by Mott for TTV.