Narrow Magnonic Waveguides Based on Domain Walls

Area of Science:

• Condensed matter physics
• Spintronics
• Materials science

Background:

• Spin waves are fundamental excitations in magnetic materials.
• Domain walls in ferromagnetic films are potential candidates for guiding these waves.
• Existing methods for spin wave propagation face limitations in miniaturization and control.

Purpose of the Study:

• To theoretically and computationally demonstrate spin wave channeling along domain walls in ultrathin ferromagnetic films.
• To investigate the properties of these channeled spin waves, including their localization, frequency, and propagation behavior.
• To explore the influence of Dzyaloshinskii-Moriya interaction on the channeling and its potential for nonreciprocal wave propagation.

Main Methods:

• Theoretical modeling of spin wave dynamics in ferromagnetic films.
• Micromagnetics simulations to visualize and analyze spin wave propagation along domain walls.
• Analysis of frequency gaps and mode localization.

Main Results:

• Demonstrated theoretical and simulated channeling of spin waves localized to domain walls.
• Observed that these channeled modes exist in the frequency gap of bulk spin wave modes.
• Showed that channeled spin waves can be guided in curved geometries and propagate closely spaced.
• Identified strong nonreciprocity and high group velocities (exceeding 1 km/s) for Néel-type walls due to Dzyaloshinskii-Moriya interaction.
• Found that a strong Dzyaloshinskii-Moriya interaction can lead to mode degeneracy.

Conclusions:

• Domain walls in ultrathin ferromagnetic films can effectively channel spin waves, analogous to whispering gallery waves.
• The Dzyaloshinskii-Moriya interaction introduces significant nonreciprocity and potential for high-speed, one-dimensional waveguiding.
• This research opens avenues for developing novel spintronic devices utilizing controlled spin wave propagation along domain walls.