Ultrafast propagation of magnon-polaritons

TL;DR

This paper demonstrates that magnon-polaritons in yttrium iron garnet films can propagate at speeds exceeding 100 km/s, enabling ultrafast spintronic information transfer far beyond conventional spin waves.

Contribution

It provides experimental evidence and theoretical modeling of ultrafast magnon-polariton propagation in garnet films, revealing their potential for high-speed spintronic applications.

Findings

Magnon-polaritons propagate faster than 100 km/s.

Propagation distances exceed 40 micrometers in 20 nm films.

Magnon-polaritons can manipulate magnetization and domain walls.

Abstract

The manipulation of magnetization lies at the heart of spintronic and magnonic technologies, with the ultimate performance of such systems limited by the velocity at which magnetic excitations can propagate. Here, we demonstrate ultrafast propagation of magnon-polaritons-hybrid quasiparticles arising from the coupling between spin waves and electromagnetic fields in thin pure, bismuth-, and gallium substituted yttrium iron garnet (YIG, Bi:YIG and Ga:YIG) films. Using time- and phase-resolved Brillouin light scattering microscopy and time-resolved scanning transmission microscopy, we show that magnon-polaritons can propagate faster than 100 km/s, nearly three orders of magnitude more than conventional spin waves, and can be observed at distances exceeding 40 micrometers in 20 nm thick films. Analytical modeling based on retarded Maxwell equations and Polder tensor formalism confirms the hybridized nature of the excitations and captures the nontrivial dispersion and attenuation profiles. Notably, the magnon-polaritons maintain high initial magnetization amplitudes and long decay lengths, enabling ultrafast manipulation of the magnetization far away from the excitation source. We show, that they can move domain walls or stabilize nonlinear magnetization processes. The unprecedentedly high propagation velocities make magnon-polaritons promising candidates for high-speed information transfer in future spin-based computing architectures, potentially overcoming long-standing group delay bottlenecks in magnonic logic circuits.