17 research outputs found
Mobile N\'eel skyrmions at room temperature: status and future
Magnetic skyrmions are topologically protected spin textures that exhibit
many fascinating features. As compared to the well-studied cryogenic Bloch
skyrmions in bulk materials, we focus on the room-temperature N\'eel skyrmions
in thin-film systems with an interfacial broken inversion symmetry in this
article. Specifically, we show the stabilization, the creation, and the
implementation of N\'eel skyrmions that are enabled by the electrical
current-induced spin-orbit torques. Towards the nanoscale N\'eel skyrmions, we
further discuss the challenges from both material optimization and imaging
characterization perspectives.Comment: This is an invited paper to be published in the AIP Advance
Ultrastrong Magnon-Magnon Coupling and Chiral Symmetry Breaking in a 3D Magnonic Metamaterial
Strongly-interacting nanomagnetic arrays are ideal systems for exploring the
frontiers of magnonic control. They provide functional reconfigurable platforms
and attractive technological solutions across storage, GHz communications and
neuromorphic computing. Typically, these systems are primarily constrained by
their range of accessible states and the strength of magnon coupling phenomena.
Increasingly, magnetic nanostructures have explored the benefits of expanding
into three dimensions. This has broadened the horizons of magnetic microstate
spaces and functional behaviours, but precise control of 3D states and dynamics
remains challenging.
Here, we introduce a 3D magnonic metamaterial, compatible with
widely-available fabrication and characterisation techniques. By combining
independently-programmable artificial spin-systems strongly coupled in the
z-plane, we construct a reconfigurable 3D metamaterial with an exceptionally
high 16N microstate space and intense static and dynamic magnetic coupling. The
system exhibits a broad range of emergent phenomena including ultrastrong
magnon-magnon coupling with normalised coupling rates of and magnon-magnon cooperativity up to C = 126.4, GHz
mode shifts in zero applied field and chirality-selective magneto-toroidal
microstate programming and corresponding magnonic spectral control
Controlling magnon-photon coupling in a planar geometry
The tunability of magnons enables their interaction with various other quantum excitations, including photons, paving the route for novel hybrid quantum systems. Here, we study magnon-photon coupling using a high-quality factor split-ring resonator and single-crystal yttrium iron garnet (YIG) sphere at room temperature. We investigate the dependence of the coupling strength on the size of the sphere and find that the coupling is stronger for spheres with a larger diameter as predicted by theory. Furthermore, we demonstrate strong magnon-photon coupling by varying the position of the YIG sphere within the resonator. Our experimental results reveal the expected correlation between the coupling strength and the rf magnetic field. These findings demonstrate the control of coherent magnon-photon coupling through the theoretically predicted square-root dependence on the spin density in the ferromagnetic medium and the magnetic dipolar interaction in a planar resonator