High-Angular Momentum Excitations in Collinear Antiferromagnet FePS<sub>3</sub>.

Wyzula, Jan; Mohelský, Ivan; Václavková, Diana; Kapuscinski, Piotr; Veis, Martin; Faugeras, Clément; Potemski, Marek; Zhitomirsky, Mike E et al. · Nano Lett · 2022

basic_science · Level V

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Abstract

We report on magneto-optical studies of the quasi-two-dimensional van der Waals antiferromagnet FePS<sub>3</sub>. Our measurements reveal an excitation that closely resembles the antiferromagnetic resonance mode typical of easy-axis antiferromagnets; nevertheless, it displays an unusual, four-times larger Zeeman splitting in an applied magnetic field. We identify this excitation with an |<i>S</i><sub><i>z</i></sub>| = 4 multipolar magnon─a single-ion 4-magnon bound state─that corresponds to a full reversal of a single magnetic moment of the Fe<sup>2+</sup> ion. We argue that condensation of multipolar magnons in large-spin materials with a strong magnetic anisotropy can produce new exotic states.