Microscopic origin of pressure memory in magnetite

Determine the microscopic origin of the persistent increase in the Verwey transition temperature observed in magnetite after pressure cycling and decompression, including the defect structure responsible for this pressure memory.

Background

The paper distinguishes the effects of pressure applied during measurement from those observed after pressure release. Hydrostatic pressure generally lowers the Verwey transition temperature while applied, whereas pressure cycling into the gigapascal range can leave a persistent increase in the transition temperature after decompression. The magnitude of this increase depends on the peak pressure and sample composition.

The authors identify the microscopic origin of this pressure memory as unresolved because the corresponding defect structure has not been directly imaged. Their own measurements address a different regime—remanent defects produced by uniaxial compression—and find that extended slip-related defects and residual strain fields do not measurably shift the Verwey transition.