Domain State and Temperature Dependence of Pressure Remanent Magnetization in Synthetic Magnetite: Implications for Crustal Remagnetization

Pressure remanent magnetization (PRM) is acquired when a rock is compressed in the presence of a magnetic field. This process can take place in many different environments from impact and ejection processes in space, to burial and subsequent uplifting of terrestrial rocks. In this study, we systematically study the acquisition of PRM at different pressures and temperatures, using synthetic magnetite in four different grain sizes ranging from nearly single-domain to purely multidomain. The magnitude of the PRM acquired in a 300 T field is, within error, independent of the domain state of the sample. We propose that the acquisition of a PRM is mainly driven by the magnetostriction of the magnetic material. We further show that compared to a thermal remanent magnetization, the acquisition of PRM in large multidomain grains can be quite efficient, and may represent a significant component of magnetization in low-temperature-high-pressure environments.