Magnonic Dynamics in Synthetic Antiferromagnets

Synthetic antiferromagnets (SAFs) are engineered multilayer structures in which ferromagnetic films are coupled antiferromagnetically through a non-magnetic spacer. The collective excitations of their ordered spins, known as magnons, exhibit complex dynamics governed by interlayer exchange, dipolar interactions and symmetry-breaking fields. Two principal eigenmodes emerge: the acoustic mode, in which adjacent layers precess in phase, and the optic mode, in which they precess out of phase. The tunability of these modes by structural design, external magnetic bias and interfacial engineering enables a rich spectrum of phenomena, from nonreciprocal spin-wave propagation to ultrastrong magnon–magnon coupling. Recent advances have extended resonant frequencies into the sub-terahertz regime, revealed electrically switchable magnonic responses and demonstrated coherent coupling regimes approaching deep-strong limits. These developments promise new pathways for low-dissipation information transport, on-chip signal processing and hybrid quantum technologies that exploit the unique combination of high frequencies, compact device footprints and room-temperature operation.

Research from Nature Portfolio

Recent studies have achieved room-temperature ultrastrong magnon–magnon coupling in SAFs by exploiting intrinsic asymmetries in magnetic anisotropy. The coupling strengths approach nearly the bare mode frequency, signalling entry into the deep-strong coupling regime and opening opportunities for exploring non-perturbative quantum phenomena in macroscopic spin ensembles. Elsewhere, chiral antisymmetric exchange known as the Dzyaloshinskii–Moriya interaction in layered hybrid perovskite antiferromagnets lifts parity restrictions on mode mixing. This intrinsic DMI yields magnon–magnon coupling rates that exceed dissipation, enabling robust hybridisation of acoustic and optic magnons in a highly tunable, solution-processable platform. These findings underscore the potential of synthetic antiferromagnets as versatile magnonic media for both classical and quantum information processing.

Magnonic Dynamics in Synthetic Antiferromagnets publication trend

The graph below shows the total number of articles in magnonic dynamics in synthetic antiferromagnets across all publications each year (not limited to Nature Index journals).

Technical terms

Magnon: A quantum of spin-wave excitation in a magnetically ordered medium.

Synthetic antiferromagnet (SAF): A multilayer structure in which ferromagnetic films are antiferromagnetically coupled via a non-magnetic spacer.

Acoustic mode: Collective spin precession in which magnetisations of adjacent layers oscillate in phase.

Optic mode: Collective spin precession in which adjacent layers oscillate out of phase.

Nonreciprocity: Direction-dependent propagation or frequency shift of spin waves.

Dzyaloshinskii–Moriya interaction (DMI): A chiral antisymmetric exchange interaction that induces canting and mode mixing in magnetic systems.

Ultrastrong coupling: A regime where interaction strength approaches or exceeds the resonant frequency of the coupled modes.

References

1. Ultrastrong to nearly deep-strong magnon-magnon coupling with a high degree of freedom in synthetic antiferromagnets. Nature Communications (2024).
2. Switchable giant nonreciprocal frequency shift of propagating spin waves in synthetic antiferromagnets. Science Advances (2020).
3. Zero-field Optic Mode Beyond 20 GHz in a Synthetic Antiferromagnet. Physical Review Applied (2020).
4. Hybrid magnonics in hybrid perovskite antiferromagnets. Nature Communications (2023).
5. Identification and manipulation of spin wave polarizations in perpendicularly magnetized synthetic antiferromagnets. New Journal of Physics (2021).