Critical behavior of M g1-x F ex O at the pressure-induced iron spin-state crossover

We present a high-pressure study of Mg1-xFexO (ferropericlase, Fp) single crystals 0.04(1)≤x≤0.33(1) with a focus on ferrous iron spin-state crossover and the material behavior preceding it. Using Vegard's law and highly accurate high-pressure single-crystal experimental data, we extract the lattice parameter aFeOHS of the "FeO high spin lattice contribution" in the MgO-FeO solid solution. We find that ferropericlases with a wide range of compositions share the same critical parameter aC (defined as the minimum aFeOHS after which spin crossover starts). Furthermore, we discuss the effect of composition on spin crossover in ferrous iron in ferropericlase in the limits of low and moderate concentrations of Fe2+.