A ferromagnet behaves as an atomic spin

10 Apr 2026

We have demonstrated that a non-spinning ferromagnet features gyroscopic dynamics. This concept was suggested by Maxwell in 1861, in the attempt of searching for experimental evidence of a relation between magnetism and rotation (later found in a different way by Einstein-de Haas and Barnett) but never experimentally demonstrated. In our experiment we observe two librational modes of a levitated ferromagnet and find that the angular trajectories are elliptical, which is a signature of macroscopic gyromagnetic coupling. A full gyroscopic behaviour is expected for smaller nanomagnets, leading eventually to atomic-like dynamics, such as a macroscopic Larmor precession in an external field.  Our paper has been published in Physical Review Letters and has got a quite huge impact: the paper has been selected as Editor's Suggestion and featured on APS Physics and on several other journals and websites: Nature, Phys.org, Science Uncovered, Società Italiana di Fisica.

Ultrasensitive Magnetometry

18 March 2025

We have realized a magnetometer based on a levitated ferromagnet in a superconducting trap, capable of overcoming the so called Energy Resolution Limit, a recently proposed benchmark for magnetometry which turns out to coincide with the standard quantum limit for most classes of magnetometers. Our magnetometer works in classical regime but can outperform most quantum limited sensors. In fact, the quantum limit of a mechanically-detected ferromagnetic sensor is orders of magnitude lower. Interestingly, our sensor can be seen as a modern version of the first magnetometer of history developed by Carl Friedrich Gauss in 1833. Therefore, we have indirectly shown that Gauss magnetometer is still, in some sense, the best on the market. Our paper has been published in Physical Review Letters.