Thermally Induced Anomaly in the Shear Behavior of Magnetite at High Pressure

Abstract

Understanding the crystal structure, phase stability, and elasticity of magnetite (Fe${}_{3}$O${}_{4}$) at high pressure and temperature will explain the behavior of the Fe-O system deep within the Earth, and promote applications and engineering of Fe-O under extreme conditions. Using ultrasonic interferometry plus $i\phantom{\rule{0}{0ex}}n$ $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ x-ray techniques, the authors discover a temperature-driven anomaly in magnetite's shear behavior and a pressure-induced softening of its shear modulus, due to local atomic distortions and charge ordering of Fe cations at the octahedral sites in the inverse-spinel structure. This work will interest researchers in physics, chemistry, materials science, and geoscience.