Magnetic, Electronic and Structural Transitions in Iron Bearing Minerals under Pressure: Theory and Experiment

点击翻译按钮获取中文摘要

Iron bearing minerals play an important role in both geosciences and technology. For example, species of the magnetite-ülvospinel solid solution series are the principle carriers of remanent magnetization in the Earth’s crust. Moreover, the iron oxyhydroxides can be regarded as a model system to explore the effect of hydrous Fe-bearing minerals at conditions of the Earth’s crust and mantle. The goal of our project is to investigate the structure-property relation in iron bearing minerals at extreme conditions by combining state of the art density functional theory (DFT) calculations with experimental techniques. In particular we focus on the interplay between structural and magnetic phase transitions, possible changes in electronic properties (e.g. metal-to-insulator transitions) as well as spin-crossover phenomena. Three study targets are selected. 1) The recently proposed pressure-induced inverse-to-normal spinel transition in magnetite. 2) The variation of magnetic properties of titanomagnetite under pressure as a function of titanium concentration. 3) The role of light elements in pressure-induced phase transitions and possible spin-crossover in iron (oxy)hydroxides. To address these issues we will employ first principles methods taking into account electronic correlations beyond band theory, as well as experimental procedures that are designed to bridge the gap between approaches used in the solid-state physics community, notably Mössbauer and diffraction methods, with those applied in geophysics, where understanding the origin of magnetic remanence is of prime importance.