Abstract
Magnons (the quanta of spin waves) could be used to encode information in beyond Moore computing applications. In this study, the magnon coupling between acoustic mode and optic mode in synthetic antiferromagnets (SAFs) is investigated by micromagnetic simulations. For a symmetrical SAF system, the time-evolution magnetizations of the two ferromagnetic layers oscillate in-phase at the acoustic mode and out-of-phase at the optic mode, showing an obvious crossing point in their antiferromagnetic resonance spectra. However, the symmetry breaking in an asymmetrical SAF system by the thickness difference, can induce an anti-crossing gap between the two frequency branches of resonance modes and thereby a strong magnon-magnon coupling appears between the resonance modes. The magnon coupling induced a hybridized resonance mode and its phase difference varies with the coupling strength. The maximum coupling occurs at the bias magnetic field at which the two ferromagnetic layers oscillate with a 90° phase difference. Besides, we show how the resonance modes in SAFs change from the in-phase state to the out-of-phase state by slightly tuning the magnon-magnon coupling strength. Our work provides a clear physical picture for the understanding of magnon-magnon coupling in a SAF system and may provide an opportunity to handle the magnon interaction in synthetic antiferromagnetic spintronics.
Highlights
Magnon spintronics [1], which utilize propagating spin waves for nanoscale transmission and processing of information, have been growing as emerging research fields [2]
We find that a clear frequency crossing between the optic and acoustic magnon modes appear in a symmetrical synthetic antiferromagnets (SAFs), indicating the absence of magnon coupling due to symmetry protection
We study the dynamics of antiferromagnetic resonance
Summary
Magnon spintronics [1], which utilize propagating spin waves for nanoscale transmission and processing of information, have been growing as emerging research fields [2]. Due to the presence of two sublattices in antiferromagnets (AFMs) or ferrimagnets, the ferromagnetic resonance (FMR) spectra possess two different magnon branches. These two magnon modes can merge into a single branch at a degeneracy point, at which strong magnon-magnon interactions occur. It was shown that in a symmetrical SAF the symmetry-protected mode crossing in FMR spectra between the acoustic and optic mode branches can be eliminated by a tilting bias magnetic field [22,23] or by dynamic dipolar interaction from nonuniform precession of magnetic moments [24]. An obvious feature of the magnon hybridization state is the appearance of an anti-crossing gap in frequency spectra between the acoustic and optic branches.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
