magnetometry

Magnetometry is the measurement of magnetic fields. A magnetometer is the instrument used for such measurements. Measurements can be scalar, reporting only the magnitude of the magnetic flux density, or vector, providing the components of the field in a chosen coordinate system. Common field units include tesla and nanotesla.

Technologies used to perform magnetometry range from cryogenic to room-temperature sensors. Superconducting quantum interference devices (SQUIDs) offer extreme sensitivity but require cooling to cryogenic temperatures. Fluxgate magnetometers are robust and widely used for low-frequency fields and navigation. Hall effect sensors rely on the Hall voltage generated by charge carriers in a conductor. Magnetoresistive devices exploit changes in electrical resistance in ferromagnetic multilayers (AMR, GMR, TMR). Optically pumped magnetometers use atomic vapors to detect spin precession, achieving high sensitivity at room temperature. Nitrogen-vacancy centers in diamond provide quantum-enhanced sensing with high spatial resolution for nanoscale measurements.

Applications include geophysical field mapping and magnetic anomaly detection, archaeology and mineral prospecting, nondestructive testing, biomagnetism (for example, magnetoencephalography and magnetocardiography), and navigation. In research, magnetometry supports studies of geomagnetic variation, material properties, and tests of fundamental physics. Performance is governed by sensitivity, bandwidth, and environmental noise, with shielding or calibration often required to mitigate interference.