Magnetization measurements using SQUID with diamond anvil cells under extremely high pressure

The crystal structures of the studied materials can be manipulated under a compression field. Combining a high-pressure apparatus with a low-temperature cryostat requires the design of a compact-scale high-pressure apparatus which generally results in reduced sample volume. In the magnetic measurements, this requires the use of a superconducting quantum interference device (SQUID), which is a highly sensitive magnetic device for detecting changes in minute magnetic fluxes. In this review, two types of SQUID magnetometers for pressure (P) of up to 30 GPa are reviewed. One is a commercial SQUID magnetometer with a miniature diamond anvil cell (DAC) covering a wide temperature range of 1.8–400 K, and the other is a vibrating-coil SQUID magnetometer equipped with DAC, which provides more accurate measurements. The former was used for oxygen molecules, molecule-based magnets, permanent magnets, organic radial ferromagnets, and lanthanide ferromagnets, whereas the latter was applied to organic radial ferromagnets, samarium (Sm), and an iron-based superconductor. Further developments of accurate magnetization measurements at high pressures are important for condensed matter studies on magnets and superconductors.