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Revealing Pressure-Induced Anomaly in Sound Velocities, and New Thermoelasticity of α-Fe2O3 Hematite at High Pressure: Implications for the Earth’s Interior
  • Yongtao Zou
Yongtao Zou
Shenzhen Technology University

Corresponding Author:[email protected]

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Elastic wave velocities of polycrystalline hematite have been measured at simultaneously high pressures and temperatures up to 6.5 GPa and 1100 K using ultrasonic interferometry in conjunction with synchrotron X-ray techniques. Here, a pronounced pressure-induced anomaly in the shear wave velocity of hematite is observed at ~3.5 GPa and 300 K, which is attributed to the occurrence of (weak)ferromagnetic-to-antiferromagnetic Morin transition of hematite upon compression. By contrast, this anomalous behavior in VS at high pressure is unexpected absence in VP. With further increase of pressures and temperatures up to 6.5 GPa and 1100 K, no apparent discontinuity is observed in sound velocities, probably resulting from the Néel transition in hematite. Using two-dimensional linear fitting approaches, the bulk and shear moduli and their pressure and temperature dependences for hematite are derived. These findings and new high-P thermoelasticity data will be of significant importance for its geophysical and materials science implications.