Magnetodielectric detection of magnetic quadrupole order in Ba(TiO)Cu<sub>4</sub>(PO<sub>4</sub>)<sub>4</sub> with Cu<sub>4</sub>O<sub>12</sub> square cupolas.
basic_science · Level V
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- Record sourced from PubMed, PMID 27698426.
- Also identified by DOI 10.1038/ncomms13039 and PMC identifier 5059463.
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Abstract
In vortex-like spin arrangements, multiple spins can combine into emergent multipole moments. Such multipole moments have broken space-inversion and time-reversal symmetries, and can therefore exhibit linear magnetoelectric (ME) activity. Three types of such multipole moments are known: toroidal; monopole; and quadrupole moments. So far, however, the ME activity of these multipole moments has only been established experimentally for the toroidal moment. Here we propose a magnetic square cupola cluster, in which four corner-sharing square-coordinated metal-ligand fragments form a noncoplanar buckled structure, as a promising structural unit that carries an ME-active multipole moment. We substantiate this idea by observing clear magnetodielectric signals associated with an antiferroic ME-active magnetic quadrupole order in the real material Ba(TiO)Cu<sub>4</sub>(PO<sub>4</sub>)<sub>4</sub>. The present result serves as a useful guide for exploring and designing new ME-active materials based on vortex-like spin arrangements.