I. S. Lyubutin, A. G. Gavriliuk, K. V. Frolov, J. F. Lin, I. A. Trojan, “High-spin-low-spin transition in magnesiowüstite (Mg$_{0.75}$Fe$_{0.25}$)O at high pressures under hydrostatic conditions”, Pis'ma v Zh. Èksper. Teoret. Fiz., 2009, Volume 90, Issue 9,Pages 681

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CONDENSED MATTER

High-spin-low-spin transition in magnesiowüstite (Mg$_{0.75}$Fe$_{0.25}$)O at high pressures under hydrostatic conditions

I. S. Lyubutin^ab, A. G. Gavriliuk^bc, K. V. Frolov^b, J. F. Lin^d, I. A. Trojan^b

^a Russian Research Centre "Kurchatov Institute"
^b Institute of Cristallography RAS
^c Institute for High Pressure Physics RAS
^d Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712-0254, USA

Abstract: The spin states of Fe$^{2+}$ ions in (Mg$_{0.75}$,Fe$_{0.25}$)O magnesiowüstite crystals at hydrostatic pressures up to 90 GPa created in a diamond-anvil cell with helium as a pressure-transmitting medium have been investi-gated by transmission and synchrotron Mössbauer spectroscopy at room temperature. An electron transition from the high-spin (HS) state to the low-spin (LS) state (HS-LS crossover) has been observed in the pressure range of 55–70 GPa. The true HS-LS transition occurs in a narrow pressure range and the extension of the electron transition to $\sim$15 GPa is attributed to the effect of the nearest environment and to thermal fluctuations between the high-spin and low-spin states at finite temperatures. It has been found that the lowest pressure at which the electron HS-LS transition can occur in the Mg$_{1-x}$Fe$_x$ system is 50–55 GPa.

PACS: 74.62.Fj, 75.50.-y, 78.70.En, 81.40.Rs

Received: 01.10.2009