Wide-range wavevector selectivity of magnon gases in Brillouin light scattering spectroscopy

Abstract

Brillouin light scattering spectroscopy is a powerful technique for the study of fast magnetization dynamics with both frequency and wavevector resolutions. Here, we report on a distinct improvement of this spectroscopic technique toward two-dimensional wide-range wavevector selectivity in a backward scattering geometry. Spin-wave wavevectors oriented perpendicularly to the bias magnetic field are investigated by tilting the sample within the magnet gap. Wavevectors which are oriented parallel to the applied magnetic field are analyzed by turning the entire setup, including the magnet system. The setup features a wide selectivity of wavevectors up to 2.04x10(5) rad/cm for both orientations, and allows selecting and measuring wavevectors of dipole- and exchange-dominated spin waves of any orientation to the magnetization simultaneously.

Bose–Einstein condensation in an ultra-hot gas of pumped magnons

“…These measurements were performed using a rotating sample stage as described in ref. 31 with a wavenumber resolution DqD0.4 Â 10 4 cm À 1 . In the case of a low pumping power of 1 W-corresponding to the case of a moderate heating of the magnon gas-a clear concentration of magnons occurs at the global energy minimum (compare Figs 4a and 6a) q ¼ 4 Â 10 4 cm À 1 .…”

“…Due to geometrical constraints of the rotating stage, the magnons are detected up to q ¼ 1.1 Â 10 5 cm À 1 with wavenumber resolution of DqC0.4 Â 10 4 cm À 1 (ref. 31). The frequency resolution of our BLS measurements is 150 MHz.…”

Thermalization of magnons in yttrium-iron garnet: Nonequilibrium functional renormalization group approach

“…A particularly well characterized magnet is yttrium-iron garnet (YIG) 21 . The momentum distribution function of the magnon gas in YIG has been probed experimentally using the technique of Brillouin light scattering 6,22,23,39 . At long wavelengths the energy dispersion of the experimentally relevant magnon band in thin YIG-stripes can be approximated by Eq.…”

Excitation of the three principal spin waves in yttrium iron garnet using a wavelength-specific multi-element antenna

“…1,2 By exploiting this property, along with number-conserving internal scattering processes, it is reported that Bose-Einstein condensation (BEC) of magnons can be achieved in YIG films with thicknesses of a few microns. 3 Brillouin light scattering, 4,5 which was used in the BEC experiments, has proven to be a powerful tool to characterize short wavelength spin waves launched from stripline antennas and, more broadly, their distribution under thermal equilibrium and non-equilibrium conditions. But if devices based on short wavelength magnons are to emerge, it is anticipated that techniques to strongly couple to directed spin waves in a wavelength-specific manner will be required, and towards this end we are experimenting with multi-element antennas to generate and detect such waves.…”