Spin-Wave Dispersion Measurement by Variable-Gap Propagating Spin-Wave Spectroscopy

Knowledge of the spin-wave dispersion relation is a prerequisite for explanation many magnonic phenomena as well practical design devices. Spin-wave measurement by established optical techniques such Brillouin light scattering or magneto-optical Kerr effect at ultralow temperatures often forbiddingly complicated. By contrast, microwave spectroscopy can be used all but it usually lacks spatial and wave-number resolution. Here we develop variable-gap-propagating-spin-wave-spectroscopy (VGPSWS) method deduction spin waves in wide frequency range. The based on phase-resolved analysis transmission between two antennas with variable spacing, conjunction theoretical data treatment. We validate in-plane magnetized $\mathrm{Co}$-$\mathrm{Fe}$-$\mathrm{B}$ yttrium iron garnet thin films $\mathbf{k}\ensuremath{\perp}\mathbf{B}$ $\mathbf{k}\ensuremath{\parallel}\mathbf{B}$ geometries deducing full set material parameters, including dispersion, hybridization fundamental mode higher-order perpendicular standing modes, surface pinning. compatibility microwaves low makes this approach attractive cryogenic magnonics nanoscale.