Publication at Faculty of Mathematics and Physics |
2022
Abstract
We report on magneto-optical studies of the quasi-two-dimensional van der Waals antiferromagnet FePS(3). 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 |S(z)| = 4 multipolar magnon-a single-ion 4-magnon bound state -that corresponds to a full reversal of a single magnetic moment of the Fe(2+) ion. We argue that condensation of multipolar magnons in large-spin materials with a strong magnetic anisotropy can produce new exotic states.