Mechanical Magnetometry with a Levitated Magnet

Levitated systems have emerged as powerful platforms for precision sensing, enabling the detection of weak forces, torques, and magnetic and electric fields. We demonstrate a magnetometer based on a micrometer-scale permanent magnet levitated above a type-II superconductor. The magnet's librational and translational modes exhibit high mechanical quality factors and couple directly to external magnetic fields and field gradients through its large intrinsic magnetic moment. The measured magnetic field sensitivity is limited by the thermal fluctuations of the levitated magnet. Notably, we experimentally achieve a magnetic field sensitivity beyond the energy resolution limit (ERL), a practical quantum limit applicable to most conventional magnetometers. We further discuss measurement schemes for both ac and dc magnetometry. These results establish a new regime of magnetic sensing, opening avenues for probing new physics and detecting dark matter, and highlight the potential of using levitated magnets as powerful local probes for microscopic magnetic phenomena in materials science.