For a magnet to stick to a fridge door, several physical effects inside of it need to work together perfectly. The magnetic moments of its electrons all point in the same direction, even if no external magnetic field forces them to do so.
This happens because of the so-called exchange interaction, a combination of electrostatic repulsion between electrons and quantum mechanical effects of the electron spins, which, in turn, are responsible for the magnetic moments. This is a common explanation for the fact that certain materials like iron or nickel are ferromagnetic or permanently magnetic, as long as one does not heat them above a particular temperature.
At ETH in Zurich, a team of researchers led by Ataç Imamoğlu at the Institute for Quantum Electronics and Eugene Demler at the Institute for Theoretical Physics have now detected a new type of ferromagnetism in an artificially produced material, in which the alignment of the magnetic moments comes about in a completely different way. They recently published their results in the journal Nature.
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