The idea that magnetism doesn’t necessarily always have a dipolar configuration is not a new one, but it’s not an easy theory to find evidence for. Most recently a team of scientists at the University of Toronto used a new method involving vibrational energy in the form of phonons to find evidence for an octupolar magnetic order.

In the associated paper in Physical Review Letters (paywalled, arXiv version) by [Ruairidh Sutcliffe] et al. we can find more details on this method and what their findings may mean for various fields. Naturally, this is a quantum-level phenomenon that requires Raman spectroscopy to be detectable via said phonons.

The materials investigated here are also somewhat exotic, ranging from actinides like NpO₂ to transition metal oxides like Sr₂MgReO₆, while having on common strong spin-orbit coupling. Where the phonons come into play is that they can be used to indirectly measure crystal lattice distortions due to the pseudo-angular momentum assigned to the phonons. This generates pseudo-chiral phonons which then show up in the Raman spectroscopy.

Although finding evidence for octopolar magnetic order is interesting in itself, this way to measuring a crystal lattice’s structure makes for another fascinating research tool that can be used to study many similar phenomenon.

These quantum-level magnetic states could conceivably be used for anything from sensors to magnetic data storage, though any such research is unlikely to be commercialized any time soon.