Researchers at the University of Toronto have detected an unusual magnetic order defined by eight poles, not the typical two, using a novel method of probing atomic vibrations with light. The team identified, within a crystalline structure, a magnetic state previously difficult to observe. “We identified new signatures of a hidden type of magnetic state which cannot be detected using ordinary probes,” says Arun Paramekanti, a professor. This discovery, published in Physical Review Letters, establishes a pathway to potentially harnessing this multi-polar magnetism for applications like controllable read-write memory elements.
Light-Induced Phonon Signatures Reveal Octupolar Magnetism
Chiral phonons, atomic vibrations exhibiting distinct “handedness” like left and right hands, served as the key to detecting a previously elusive magnetic order at the University of Toronto. Researchers discovered these pseudo-chiral phonons, vibrations behaving uniquely in comparison to conventional magnets, reveal the presence of octupolar magnetism, a state defined by eight poles rather than the usual two.
Swati Chaudhary, a project research associate and study co-author, explains that these vibrations “provide a new way of identifying and studying hidden magnetic states.” The team’s method relies on directing rotating light at crystalline materials, triggering atomic vibrations and observing the resulting optical fingerprint of the magnetic order. This approach bypasses the limitations of standard magnetic detection techniques, which struggle to identify these complex, multi-polar arrangements.
Lead author Rory Sutcliffe, a PhD candidate, clarifies that chiral phonons “have a ‘handedness’ and exist in distinct, non-matching forms,” and this property is important to the detection process. The researchers found that the emergence of octupolar order directly influences these phonon modes, imbuing them with a measurable chirality.
Kathleen Hart, also a PhD candidate, explains that “Our work offers a new optical probe of hidden magnetic orders that are difficult to detect by standard techniques and lays the foundation for how such octupolar magnetism might eventually be controlled through atomic vibrations within a material.” The findings published in Physical Review Letters demonstrate a novel technique for not only observing but potentially manipulating these complex magnetic states.
Our work offers a new optical probe of hidden magnetic orders that are difficult to detect by standard techniques and lays the foundation for how such octupolar magnetism might eventually be controlled through atomic vibrations within a material.
Kathleen Hart, also a PhD candidate in U of T’s department of physics and study co-author
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