Nonreciprocal collective magnetostatic wave modes in geometrically asymmetric bilayer structure with nonmagnetic spacer

Abstract

Nonreciprocity, i.e. inequivalence in amplitudes and frequencies of spin waves propagating in opposite directions, is a key property underlying functionality in prospective magnonic devices. Here we demonstrate experimentally and theoretically a simple approach to induce frequency nonreciprocity in a magnetostatically coupled ferromagnetic bilayer structure with a nonmagnetic spacer by its geometrical asymmetry. Using Brillouin light scattering, we show the formation of two collective spin wave modes in Fe${}_{81}$Ga${}_{19}$/Cu/Fe${}_{81}$Ga${}_{19}$ structure with different thicknesses of ferromagnetic layers. Experimental reconstruction and theoretical modeling of the dispersions of acoustic and optical collective spin wave modes reveal that both possess nonreciprocity reaching several percent at the wavenumber of $22\cdot 10^4$ rad cm${}^{-1}$. The analysis demonstrates that the shift of the amplitudes of counter-propagating coupled modes towards either of the layers is responsible for the nonreciprocity because of the pronounced dependence of spin wave frequency on the layers thickness. The proposed approach enables the design of multilayered ferromagnetic structures with a given spin wave dispersion for magnonic logic gates.

arXiv comment6 pages, 3 figures, 1 supplementary materials file

References in corpus (21)

• Spin-Wave Propagation in the Presence of Interfacial Dzyaloshinskii-Moriya Interaction
• An Introduction to Spin Wave Computing
• Asymmetric Spin-wave Dispersion on Fe(110): Direct Evidence of Dzyaloshinskii--Moriya Interaction
• Hybrid magnonics: physics, circuits and applications for coherent information processing
• Chiral asymmetry of the spin-wave spectra in ultrathin magnetic films
• Nonreciprocal spin wave propagation in chiral-lattice ferromagnets
• Frequency non-reciprocity of surface spin wave in Permalloy thin films
• Spin pinning and spin-wave dispersion in nanoscopic ferromagnetic waveguides
• Tunable magnon-magnon coupling in synthetic antiferromagnets
• Spin-wave diode and circulator based on unidirectional coupling
• Slow-wave based magnonic diode
• Flat Bands, Indirect Gaps, and Unconventional Spin-Wave Behavior Induced by a Periodic Dzyaloshinskii-Moriya Interaction
• Magnonic band gaps in YIG based magnonic crystals: array of grooves versus array of metallic stripes
• Chemical potential of quasi-equilibrium magnon gas driven by pure spin current
• Optical excitation of propagating magnetostatic waves in an epitaxial Galfenol film by an ultrafast magnetic anisotropy change
• Nonreciprocal Emergence of Hybridized Magnons in magnetic thin Films
• Exchange coupling and magnetoresistance in CoFe/NiCu/CoFe spin-valves near the Curie point of the spacer
• Effect of magnetic anisotropy relaxation on laser-induced magnetization precession in thin galfenol films
• Optically driven spin pumping mediating collective magnetization dynamics in a spin valve structure
• Backward magnetostatic surface spin waves in exchange coupled Co/FeNi bilayers
• Optical excitation of single- and multi-mode magnetization precession in Galfenol nanolayers