Iron is the most abundant transition-metal element in the mantle and therefore plays an important role in the geochemistry and geodynamics of the Earth's interior1,2,3,4,5,6,7,8,9,10,11. Pressure-induced electronic spin transitions of iron occur in magnesiowüstite, silicate perovskite and post-perovskite1,2,3,4,8,10,11. Here we have studied the spin states of iron in magnesiowüstite and the isolated effects of the electronic transitions on the elasticity of magnesiowüstite with in situ X-ray emission spectroscopy and X-ray diffraction to pressures of the lowermost mantle. An observed high-spin to low-spin transition of iron in magnesiowüstite results in an abnormal compressional behaviour between the high-spin and the low-spin states. The high-pressure, low-spin state exhibits a much higher bulk modulus and bulk sound velocity than the low-pressure, high-spin state; the bulk modulus jumps by ∼35 per cent and bulk sound velocity increases by ∼15 per cent across the transition in (Mg0.83,Fe0.17)O. Although no significant density change is observed across the electronic transition, the jump in the sound velocities and the bulk modulus across the transition provides an additional explanation for the seismic wave heterogeneity in the lowermost mantle12,13,14,15,16,17,18,19,20,21. The transition also affects current interpretations of the geophysical and geochemical models using extrapolated or calculated thermal equation-of-state data without considering the effects of the electronic transition5,6,22,23.
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Sherman, D. M. in Structural and Magnetic Phase Transitions in Minerals (eds Ghose, S., Coey, J. M. D. & Salje, E.) 113–118 (Springer, New York, 1988)
Sherman, D. M. The high-pressure electronic structure of magnesiowüstite (Mg,Fe)O: applications to the physics and chemistry of the lower mantle. J. Geophys. Res. 96(B9), 14299–14312 (1991)
Sherman, D. M. & Jansen, H. J. F. First-principles predictions of the high-pressure phase transition and electronic structure of FeO: implications for the chemistry of the lower mantle and core. Geophys. Res. Lett. 22, 1001–1004 (1995)
Cohen, R. E., Mazin, I. I. & Isaak, D. G. Magnetic collapse in transition metal oxides at high pressure: implications for the Earth. Science 275, 654–657 (1997)
Mao, H. K., Shen, G. & Hemley, R. J. Multivariable dependence of Fe-Mg partitioning in the lower mantle. Science 278, 2098–2100 (1997)
Andrault, D. Evaluation of (Mg,Fe) partitioning between silicate perovskite and magnesiowüstite up to 120 GPa and 2300 K. J. Geophys. Res. 106, 2079–2087 (2001)
Kesson, S. E., Fitz Gerald, J. D., O'Neill, H., St, C. & Shelley, J. M. G. Partitioning of iron between magnesian silicate perovskite and magnesiowüstite at about 1 Mbar. Phys. Earth Planet. Inter. 131, 295–310 (2002)
Badro, J. et al. Iron partitioning in Earth's mantle: toward a deep lower mantle discontinuity. Science 300, 789–791 (2003)
Lin, J. F. et al. Stability of magnesiowüstite in the Earth's lower mantle. Proc. Natl Acad. Sci. USA 100, 4405–4408 (2003)
Badro, J. et al. Electronic transitions in perovskite: possible nonconvecting layers in the lower mantle. Science 305, 383–386 (2004)
Li, J. et al. Electronic spin state of iron in lower mantle perovskite. Proc. Natl Acad. Sci. USA 101, 14027–14030 (2004)
Su, W. J. & Dziewonski, A. M. Simultaneous inversion for 3-D variations in shear and bulk velocity in the mantle. Phys. Earth Planet. Inter. 100, 135–156 (1997)
Kellogg, L. H., Hager, B. H. & van der Hilst, R. D. Compositional stratification in the deep mantle. Science 283, 1881–1884 (1999)
van der Hilst, R. D. & Kárason, H. Compositional heterogeneity in the bottom 1000 kilometers of Earth's mantle: toward a hybrid convection model. Science 283, 1885–1888 (1999)
Garnero, E. Heterogeneity of the lowermost mantle. Annu. Rev. Earth Planet. Sci. 28, 509–537 (2000)
Masters, G., Laske, G., Bolton, H. & Dziewonski, A. M. in Earth's Deep Interior: Mineral Physics and Tomography From the Atomic to the Global Scale (eds Karato, S., Forte, A. M., Liebermann, R. C., Masters, G. & Stixrude, L.) 63–87 (American Geophysical Union, Washington DC, 2000)
Karato, S. I. & Kaiki, B. B. Origin of lateral variation of seismic wave velocities and density in the deep mantle. J. Geophys. Res. 106, 21771–21783 (2001)
Lay, T., Garnero, E. J. & Williams, Q. Partial melting in a thermo-chemical boundary layer at the base of the mantle. Phys. Earth Planet. Inter. 146, 441–467 (2004)
Murakami, M., Hirose, K., Kawamura, K., Sata, N. & Ohishi, Y. Post-perovskite phase transition in MgSiO3 . Science 304, 855–858 (2004)
Oganov, A. R. & Ono, S. Theoretical and experimental evidence for a post-perosvkite phase of MgSiO3 in Earth's D″ layer. Nature 430, 445–448 (2004)
Tsuchiya, T., Tsuchiya, J., Umemoto, K. & Wentzcovitch, R. M. Elasticity of post-perovskite MgSiO3 . Geophys. Res. Lett. 31, L14603, doi:10.1029/2004GL020278 (2004)
Jackson, I. Elasticity, composition and temperature of the Earth's lower mantle: a reappraisal. Geophys. J. Int. 134, 291–311 (1998)
Stacey, F. D. & Isaak, D. G. Compositional constraints on the equation of state and thermal properties of the lower mantle. Geophys. J. Int. 146, 143–154 (2001)
Jacobsen, S. D. et al. Structure and elasticity of single-crystal (Mg,Fe)O and a new method of generating shear waves for gigahertz ultrasonic interferometry. J. Geophys. Res. 107(B2), 10.1029/2001JB000490 (2002)
Speziale, S., Zha, C. S., Duffy, T. S., Hemley, R. J. & Mao, H. K. Quasi-hydrostatic compression of magnesium oxide to 52 GPa: Implications for the pressure-volume-temperature equation of state. J. Geophys. Res. 106, 515–528 (2001)
Holmes, N. C., Moriarty, J. A., Gathers, G. R. & Nellis, W. J. The equation of state of platinum to 660 GPa (6.6 Mbar). J. Appl. Phys. 66, 2962–2967 (1989)
Birch, F. Equation of state and thermodynamic parameters of NaCl to 300 kbar in the high-temperature domain. J. Geophys. Res. 91, 4949–4954 (1986)
Vinet, P., Ferrante, J., Rose, J. H. & Smith, J. R. Compressibility of solids. J. Geophys. Res. 92, 9319–9325 (1987)
Shannon, R. D. & Prewitt, C. T. Effective ionic radii in oxides and fluorides. Acta Crystallogr. B25, 925–946 (1969)
Badro, J. et al. Nature of the high-pressure transition in Fe2O3 hematite. Phys. Rev. Lett. 89, 205504 (2002)
Burns, R. G. Mineralogical Applications of Crystal Field Theory Ch. 2, 7–43 (Cambridge Univ. Press, Cambridge, 1993)
Brown, J. M. & Shankland, T. J. Thermodynamic parameters in the Earth as determined from seismic profiles. Geophys. J. R. Astron. Soc. 66, 579–596 (1981)
We thank R. Caracas, R. Cohen, G. Shen, V. Prakapenka, W. Sturhahn, J. M. Jackson, P. Silver, B. Militzer, S. Hardy, C. Prewitt, M. Somayazulu, P. Dera, and Y. Fei for discussions, S. J. Mackwell for help with sample synthesis, HPCAT for the use of the X-ray facilities, and GSECARS, APS, for the use of the Raman system. This work and use of the APS are supported by the US Department of Energy, Basic Energy Sciences, Office of Science and the State of Illinois under HECA. Work at Carnegie was supported by DOE/BES, DOE/NNSA (CDAC), NSF, and the W. M. Keck Foundation.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
This contains legends for Supplementary Figures S1 and S2, Supplementary Methods and Supplementary References. (DOC 37 kb)
Representative X-ray emission spectra of Fe-Kβ in magnesiowüstite [(Mg0.40,Fe0.60)O] at high pressures. (PDF 40 kb)
Relative volume of (Mg0.40,Fe0.60)O as a function of pressure at 300 K. (PDF 36 kb)
About this article
Cite this article
Lin, J., Struzhkin, V., Jacobsen, S. et al. Spin transition of iron in magnesiowüstite in the Earth's lower mantle. Nature 436, 377–380 (2005) doi:10.1038/nature03825
Elasticity of single-crystal periclase at high pressure and temperature: The effect of iron on the elasticity and seismic parameters of ferropericlase in the lower mantle
American Mineralogist (2019)
Iron isotopic fractionation in mineral phases from Earth's lower mantle: Did terrestrial magma ocean crystallization fractionate iron isotopes?
Earth and Planetary Science Letters (2019)
Charge disproportionation and site-selective local magnetic moments in the post-perovskite-type Fe2O3 under ultra-high pressures
npj Computational Materials (2019)
Effects of iron spin transition on the electronic structure, thermal expansivity and lattice thermal conductivity of ferropericlase: a first principles study
Scientific Reports (2019)
Modeling Long-Wavelength Geoid Anomalies from Instantaneous Mantle Flow: Results from Two Recent Tomography Models
Pure and Applied Geophysics (2019)