Magnetic excitations beyond the single- and double-magnons

Abstract

A photon carrying one unit of angular momentum can change the spin angular momentum of a magnetic system with one unit (ΔMs = ±1) at most. This implies that a two-photon scattering process can manipulate the spin angular momentum of the magnetic system with a maximum of two units. Herein we describe a triple-magnon excitation in α-Fe2O3, which contradicts this conventional wisdom that only 1- and 2-magnon excitations are possible in a resonant inelastic X-ray scattering experiment. We observe an excitation at exactly three times the magnon energy, along with additional excitations at four and five times the magnon energy, suggesting quadruple and quintuple-magnons as well. Guided by theoretical calculations, we reveal how a two-photon scattering process can create exotic higher-rank magnons and the relevance of these quasiparticles for magnon-based applications.

Spin wave excitations in low dimensional systems with large magnetic anisotropy

“…These results suggest that some of the two-dimensional materials considered in this work, particularly those with large magnetic anisotropy, may present a low energy spin excitation spectrum that differs significantly from the one determined by a gapless semiclassical single magnon dispersion curve. Therefore, we speculate that, in systems with large magnetic anisotropy, multi-magnon processes can play an important role in determining the low-energy magnetic excitations, although the intensity of the corresponding signal is expected to be weaker [63] and, thus, are relevant in the interpretation of the low-temperature properties of these two-dimensional ferromagnets. Its confirmation, of course, requires the use of precise and sensitive techniques, like Raman scattering [22] or FMR [15][16][17].…”

A compact approach to higher-resolution resonant inelastic x-ray scattering detection using photoelectrons

“…The sufficiently large momentum of x-rays allows mapping the dispersion of collective excitations [4][5][6][7][8]. By exploiting the photon polarization, symmetry properties of excitations can be analysed [1,[9][10][11][12][13].…”