Abstract
The stable levitation of magnets is forbidden by Earnshaw's theorem, which states that no stationary object made of magnets in a fixed configuration can be held in stable equilibrium by any combination of static magnetic or gravitational forces1,2,3. Earnshaw's theorem can be viewed as a consequence of the Maxwell equations, which do not allow the magnitude of a magnetic field in a free space to possess a maximum, as required for stable equilibrium. Diamagnets (which respond to magnetic fields with mild repulsion) are known to flout the theorem, as their negative susceptibility results in the requirement of a minimum rather than a maximum in the field's magnitude2,3,4. Nevertheless, levitation of a magnet without using superconductors is widely thought to be impossible. We find that the stable levitation of a magnet can be achieved using the feeble diamagnetism of materials that are normally perceived as being non-magnetic, so that even human fingers can keep a magnet hovering in mid-air without touching it.
References
Earnshaw, S. Trans. Camb. Phil. Soc. 7, 97–112 (1842).
Brandt, E. H. Science 243, 349–355 (1989).
Berry, M. V. & Geim, A. K. Eur. J. Phys. 18, 307–313 (1997).
Thomson, W. (Lord Kelvin) Reprints of Papers on Electrostatics and Magnetism (Macmillan, London, 1872).
Braunbeck, W. Z. Phys. 112, 753–763 (1939).
Beaugnon, E. & Tournier, R. Nature 349, 470 (1991).
Geim, A. Phys. Today 51, 36-39 (September 1998).
Arkadiev, A. Nature 160, 330 (1947).
Ikezoe, Y. et al. Nature 393, 749–750 (1998).
Simon, M. D. et al. Am. J. Phys. 65, 286–292 (1997).
Boerdijk, A. H. Philips Tech. Rev. 18, 125–127 (1956).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Geim, A., Simon, M., Boamfa, M. et al. Magnet levitation at your fingertips. Nature 400, 323–324 (1999). https://doi.org/10.1038/22444
Issue Date:
DOI: https://doi.org/10.1038/22444
- Springer Nature Limited
This article is cited by
-
Magnetic levitation using diamagnetism: Mechanism, applications and prospects
Science China Technological Sciences (2021)
-
Separation of gold and other rare materials from an ensemble of heterogeneous particles using a NdFeB magnetic circuit
Scientific Reports (2019)
-
Design of Magnetic Force Field for Trajectory Control of Levitated Diamagnetic Graphite
International Journal of Precision Engineering and Manufacturing-Green Technology (2018)
-
Magnetic separation of general solid particles realised by a permanent magnet
Scientific Reports (2016)