Effect of temperature and phase transition on intrinsic seismic wave attenuation derived from cyclic loading of neighborite (NaMgF3)

To evaluate whether the observed seismic attenuation in the lower mantle is due to small-scale lamination (extrinsic attenuation) or by intrinsic dissipation in bridgmanite and ferropericlase, we plan to conduct cyclic loading experiments on neighborite (NaMgF3) in conjunction with synchrotron radiation. NaMgF3 is a ferroelastic perovskite isostructural to bridgmanite, both belong to the sub-space-group Pbnm of the cubic perovskite structure and exhibit extensive twinning. When the direction of the stress is reversed, the perovskites will de-twin or form new twin domains. Thus, a cycling stress field causes twin domain switching and produces stress-strain hysteresis loops whose enclosed area is a measure of dissipated elastic energy. With increasing temperature, the Pbnm lattice distortion decreases, making it easier for twin domains to switch. A similar process may influence intrinsic attenuation of seismic waves travelling through bridgmanite.