A new discovery answers an old question
Now the first imaging of non-reflection domain wall structures forming in the ferroic transition of the ferrous oxide Fe0.94O has been reported by researchers from the U.S. Department of Energy Office of Sciences Advanced Photon Source (APS) and the High Pressure Synergetic Consortium (HPSynC). The team carried out the study at the 2-ID-D x-ray beamline at the APS, applying a pressure of approximately 250,000 atm in a pressure vessel called a diamond anvil cell, and imaging the materials crystalline structure using the new high-pressure nanodiffraction imaging technique developed by these researchers.
The teams results revealed a non-reflection type of domain wall structure forming due to the so-called cubic-rhombohedral transition, where the crystal structure of the material changes from cubic to rhomboidal. This discovery suggests the cubic-rhomboid transition could be associated with defects in the material and is unlikely to be caused by ferroelasticity, in which a material may develop a spontaneous strain, as predicated by previous research.
The surprising impact of defects on structural stability discovered by this study not only brings with it a new understanding of the origin of the cubic-rhomboid transition, but also underscores the need for a greater understanding of how defects in a material influences electronic and thermoelastic properties at high pressure, which has almost never been taken into consideration in previous high-pressure studies of materials.
In addition, this study demonstrates the power of the new nanodiffraction imaging technique for investigation of pressure-induced phase transitions, which has emerged as a very active area in condensed matter physics, but until now has lacked suitable in situ techniques for probing the nanoscopic origins of the transitions.