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1. Ultrastrong magnon-magnon coupling and chiral spin-texture control in a dipolar 3D multilayered artificial spin-vortex ice

   https://doi.org/10.1038/s41467-024-48080-z  

   Dion, Troy; Stenning, Kilian D.; Vanstone, Alex; Holder, Holly H.; Sultana, Rawnak; Alatteili, Ghanem; Martinez, Victoria; Kaffash, Mojtaba Taghipour; Kimura, Takashi; Oulton, Rupert F.; et al (May 2024, Nature Communications)

   Strongly-interacting nanomagnetic arrays are ideal systems for exploring reconfigurable magnonics. They provide huge microstate spaces and integrated solutions for storage and neuromorphic computing alongside GHz functionality. These systems may be broadly assessed by their range of reliably accessible states and the strength of magnon coupling phenomena and nonlinearities. Increasingly, nanomagnetic systems are expanding into three-dimensional architectures. This has enhanced the range of available magnetic microstates and functional behaviours, but engineering control over 3D states and dynamics remains challenging. Here, we introduce a 3D magnonic metamaterial composed from multilayered artificial spin ice nanoarrays. Comprising two magnetic layers separated by a non-magnetic spacer, each nanoisland may assume four macrospin or vortex states per magnetic layer. This creates a system with a rich 16^Nmicrostate space and intense static and dynamic dipolar magnetic coupling. The system exhibits a broad range of emergent phenomena driven by the strong inter-layer dipolar interaction, including ultrastrong magnon-magnon coupling with normalised coupling rates of$$\frac{\Delta f}{\nu }=0.57$$ $\frac{\Delta f}{\nu }=0.57$, GHz mode shifts in zero applied field and chirality-control of magnetic vortex microstates with corresponding magnonic spectra. 

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2. Strong Photon‐Magnon Coupling Using a Lithographically Defined Organic Ferrimagnet

   https://doi.org/10.1002/advs.202310032  

   Xu, Qin; Cheung, Hil_Fung_Harry; Cormode, Donley_S; Puel, Tharnier_O; Pal, Srishti; Yusuf, Huma; Chilcote, Michael; Flatté, Michael_E; Johnston‐Halperin, Ezekiel; Fuchs, Gregory_D (January 2024, Advanced Science)

   Abstract A cavity‐magnonic system composed of a superconducting microwave resonator coupled to a magnon mode hosted by the organic‐based ferrimagnet vanadium tetracyanoethylene (V[TCNE]_x) is demonstrated. This work is motivated by the challenge of scalably integrating a low‐damping magnetic system with planar superconducting circuits. V[TCNE]_xhas ultra‐low intrinsic damping, can be grown at low processing temperatures on arbitrary substrates, and can be patterned via electron beam lithography. The devices operate in the strong coupling regime, with a cooperativity exceeding 1000 for coupling between the Kittel mode and the resonator mode at T≈0.4 K, suitable for scalable quantum circuit integration. Higher‐order magnon modes are also observed with much narrower linewidths than the Kittel mode. This work paves the way for high‐cooperativity hybrid quantum devices in which magnonic circuits can be designed and fabricated as easily as electrical wires. 

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3. Terahertz Cavity Magnon Polaritons

   https://doi.org/10.1002/adom.202302270  

   Kritzell, T_Elijah; Baydin, Andrey; Tay, Fuyang; Rodriguez, Rodolfo; Doumani, Jacques; Nojiri, Hiroyuki; Everitt, Henry_O; Barsukov, Igor; Kono, Junichiro (December 2023, Advanced Optical Materials)

   Abstract Hybrid light–matter coupled states, or polaritons, in magnetic materials have attracted significant attention due to their potential for enabling novel applications in spintronics and quantum information processing. However, most magnon‐polariton studies in the strong coupling regime to date have been carried out for ferromagnetic materials with magnon excitations at gigahertz frequencies. Here, strong resonant photon–magnon coupling at frequencies above 1 terahertz is investigated for the first time in a prototypical room‐temperature antiferromagnetic insulator, NiO,  inside a Fabry–Pérot cavity. The cavity is formed by the crystal itself with a thickness adjusted to an optimal value. Terahertz time‐domain spectroscopy measurements in magnetic fields up to 25 T reveal the evolution of the magnon frequency through Fabry–Pérot cavity modes with photon–magnon anticrossing behavior, demonstrating clear vacuum Rabi splittings exceeding the polariton linewidths. These results show that NiO is a promising platform for exploring antiferromagnetic spintronics and cavity magnonics in the terahertz frequency range. 

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4. Mechanical Resonant Sensing of Spin Texture Dynamics in a 2D Antiferromagnet

   https://doi.org/10.1002/adma.202420168  

   Yousuf, S_M_Enamul Hoque; Wang, Yunong; Ramachandran, Shreyas; Koptur‐Palenchar, John; Tarantini, Chiara; Xiang, Li; McGill, Stephen; Smirnov, Dmitry; Santos, Elton_J G; Feng, Philip X‐L; et al (July 2025, Advanced Materials)

   Abstract The coupling between the spin degrees of freedom and macroscopic mechanical motions, including striction, shearing, and rotation, has attracted wide interest with applications in actuation, transduction, and information processing. Experiments so far have established the mechanical responses to the long‐range ordered or isolated single spin states. However, it remains elusive whether mechanical motions can couple to a different type of magnetic structure, the non‐collinear spin textures, which exhibit nanoscale spatial variations of spin (domain walls, skyrmions,etc.) and are promising candidates to realize high‐speed computing devices. Here, collective spin texture dynamics is detected with nanoelectromechanical resonators fabricated from 2D antiferromagnetic (AFM) MnPS₃with 10⁻⁹strain sensitivity. By examining radio frequency mechanical oscillations under magnetic fields, new magnetic transitions are identified with sharp dips in resonant frequency. They are attributed to collective AFM domain wall motions as supported by the analytical modeling of magnetostriction and large‐scale spin‐dynamics simulations. Additionally, an abnormally large modulation in the mechanical nonlinearity at the transition field infers a fluid‐like response due to ultrafast domain motion. The work establishes a strong coupling between spin texture and mechanical dynamics, laying the foundation for electromechanical manipulation of spin texture and developing quantum hybrid devices. 

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5. Formation of binary magnon polaron in a two-dimensional artificial magneto-elastic crystal

   https://doi.org/10.1038/s41427-023-00499-4  

   Majumder, Sudip; Drobitch, J. L.; Bandyopadhyay, Supriyo; Barman, Anjan (September 2023, NPG Asia Materials)

   Abstract We observed strong tripartite magnon-phonon-magnon coupling in a two-dimensional periodic array of magnetostrictive nanomagnets deposited on a piezoelectric substrate, forming a 2D magnetoelastic “crystal”; the coupling occurred between two Kittel-type spin wave (magnon) modes and a (non-Kittel) magnetoelastic spin wave mode caused by a surface acoustic wave (SAW) (phonons). The strongest coupling occurred when the frequencies and wavevectors of the three modes matched, leading to perfect phase matching. We achieved this condition by carefully engineering the frequency of the SAW, the nanomagnet dimensions and the bias magnetic field that determined the frequencies of the two Kittel-type modes. The strong coupling (cooperativity factor exceeding unity) led to the formation of a new quasi-particle, called a binary magnon-polaron, accompanied by nearly complete (~100%) transfer of energy from the magnetoelastic mode to the two Kittel-type modes. This coupling phenomenon exhibited significant anisotropy since the array did not have rotational symmetry in space. The experimental observations were in good agreement with the theoretical simulations. 

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