The Quantum Diamond Anvil Cell A new frontier for high pressure rock magnetism

Paleomagnetism uses the magnetic remanence of rocks to understand changes in the magnetic field through time. As such, it is critical to understand the processes by which an ancient remanence has been changed through its history. Pressure plays a vital role in the study of extraterrestrial bodies. Often meteorites, which may have experienced peak pressures of several tens of GPa, are the only source of information on their host bodies magnetic field. Therefore, reliable paleomagnetic data is required to understand how planetary bodies acquire and lose their magnetic dynamo. It is well known that pressure can alter the magnetic remanence in three ways. 1. If applied in zero-field, the remanence will be demagnetized. 2. If a magnetic field is applied during pressure cycling, a pressure remanent magnetization can overprint the original remanence. 3. The magnetic domain state can be altered to become more single domain. Until now, however, all these effects have only been observed at room pressure, after pressure cycling, or using strongly magnetic synthetic samples. The natural remanent magnetization of rock samples, on the other hand, has never been studied under pressure. Through recent developments in nitrogen-vacancy (NV) magnetometry, the quantum diamond microscope (QDM) can visualize very small magnetizations (10-16 Am2) at micrometer resolution. Here we present a new type of high-pressure magnetometer for geological samples, a fusion of a QDM with a diamond anvil cell -- the quantum diamond anvil cell (QDAC). This instrument uses a special NV imaging diamond as one of the anvils giving it the magnetic and spatial resolution of a QDM. This allows for the first time the measurement of the natural remanent magnetization of Earth and planetary materials at pressures of up to 30 GPa.We are showing preliminary data of the pressure dependence of the magnetic remanence of pyrrhotite at pressures up to 6 GPa.