Isothermal compression behavior of (Mg,Fe)O using neon as a pressure medium

• DOI: 10.1007/s00269-009-0347-6
• Publication Date: 2009-12-22T07:20:19Z
• Authors: Kirill K. Zhuravlev; J. M. Jackson; A. S. Wolf; J. K. Wicks; J. Yan; S. M. Clark
• Keywords: (Mg,Fe)O; Spin crossover; 530; 01 natural sciences; Lower mantle; Phase transition; 0105 earth and related environmental sciences

We present isothermal volume compression behavior of two polycrystalline (Mg,Fe)O samples with FeO = 39 and 78 mol% up to ~90 GPa at 300 K using synchrotron X-ray diffraction and neon as a pressure-transmitting medium. For the iron-rich (Mg0.22Fe0.78)O sample, a structural transition from the B1 structure to a rhombohedral structure was observed at 41.6 GPa, with no further indication of changes in structural or compression behavior changes up to 93 GPa. In contrast, a change in the compression behavior of (Mg0.61Fe0.39)O was observed during compression at P ≥ 71 GPa and is indicative of a spin crossover occurring in the Fe2+ component of (Mg0.61Fe0.39)O. The low-spin state exhibited a volume collapse of ~3.5%, which is a larger value than what was observed for a similar composition in a laser-heated NaCl medium. Upon decompression, the volume of the high-spin state was recovered at approximately 65 GPa. We therefore bracket the spin crossover at 65 ≤ P (GPa) ≤ 77 at 300 K (Mg0.61Fe0.39)O. We observed no deviation from the B1 structure in (Mg0.61Fe0.39)O throughout the pressure range investigated.