Nonreciprocal Emergence Of Hybridized Magnons In Magnetic Thin Films

Magnons (the quanta of spin waves), unlike electrons, do not suffer from Ohmic losses, which makes them an attractive information carrier in communication and data processing. The possibility of nonreciprocal magnon propagation is of great practical relevance to directional communications, particularly when the nonreciprocity is steerable through magnons themselves in a monologic magnonic device. This work demonstrates explicitly such nonreciprocity in the mode profiles of magnons in Ni79Fe21 thin films. Evidence of nonreciprocal emergence of hybridized dipole-exchange spin waves at two surfaces of Ni79Fe21 nanofilms deposited on a surface oxide silicon substrate is provided by studying magnon transmission and asymmetry via Brillouin light scattering measurements. The dipole-dominated spin wave and exchange-dominated spin wave are found to be localized near the top and bottom surfaces, respectively, and travel along opposite directions. The nonreciprocity and the localization can be tuned by an in-plane magnetic field. Our findings provide a simple and flexible approach to nonreciprocal all-magnon logic devices highly compatible with silicon-based integrated circuit technology.