[S-IT16] Deep Earth Sciences

[SIT16-P14] Elastic anomaly at the spin transition in ferropericlase: Revisited by GHz-DAC Ultrasonic Velocity Measurement newly developed

*Takuto Kato¹, Akira Yoneda¹, Ryo Tsuruoka¹, Tadashi Kondo¹, Daisuke Yamazaki² (1.Department of Earth and Space Science, Graduate School of Science Osaka University, 2.Institute for Planetary Materials, Okayama University)

Keywords:Diamond Anvil Cell, GHz Ultrasoni Velocity Method, Spin transtion

GHz ultrasonic velocity measurement enables us to measure elastic wave velocities of samples with ~10μm thickness compressed in diamond anvil cell (DAC). Compared with Brillouin scattering and picosecond ultrasonic, GHz method is the unique technique to measure both P wave and S wave velocities of opaque samples such as iron and its related materials.
Taking advantage of such features, we are working on sound velocity measurement of (Fe,Mg)O ferropericlase. Ferropericlase is the second most abundant mineral in the Earth's lower mantle. Previous studies have shown that ferrous ions in ferropericlase cause spin transition at pressures corresponding to the mid-mantle (40 ~ 60 GPa). This iron-spin transition affects a variety of physical properties, including viscosity and seismic wave velocity. In particular, the detection of spin transitions by velocity measurements has been shown in experiments using Brillouin scattering and inelastic X-ray scattering, but inconsistency remains in previous studies (Yan et al. 2015, Antonangeli et al.).
In this presentation, we would introduce the progress of the GHz method and report the sound velocity measurement results of ferropericlase.