Ferromagnet/Superconductor Hybrid Magnonic Metamaterials

• Published in: Advanced science Vol. 6; no. 16; pp. 1900435 - n/a
• Main Authors: Golovchanskiy, Igor A., Abramov, Nikolay N., Stolyarov, Vasily S., Dzhumaev, Pavel S., Emelyanova, Olga V., Golubov, Alexander A., Ryazanov, Valery V., Ustinov, Alexey V.
• Format: Journal Article
• Language: English
• Published: Germany John Wiley & Sons, Inc 21.08.2019; John Wiley and Sons Inc; Wiley
• Subjects: ferromagnetic resonance; Fourier transforms; Geometry; Magnetic fields; magnonic crystals; Numerical analysis; Propagation; spin waves; superconductivity; Thin films; spin waves; superconductivity; magnonic crystals; ferromagnetic resonance
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.201900435

In this work, a class of metamaterials is proposed on the basis of ferromagnet/superconductor hybridization for applications in magnonics. These metamaterials comprise of a ferromagnetic magnon medium that is coupled inductively to a superconducting periodic microstructure. Spectroscopy of magnetization dynamics in such hybrid evidences formation of areas in the medium with alternating dispersions for spin wave propagation, which is the basic requirement for the development of metamaterials known as magnonic crystals. The spectrum allows for derivation of the impact of the superconducting structure on the dispersion: it takes place due to a diamagnetic response of superconductors on the external and stray magnetic fields. In addition, the spectrum displays a dependence on the superconducting critical state of the structure: the Meissner and the mixed states of a type II superconductor are distinguished. This dependence hints toward nonlinear response of hybrid metamaterials on the magnetic field. Investigation of the spin wave dispersion in hybrid metamaterials shows formation of allowed and forbidden bands for spin wave propagation. The band structures are governed by the geometry of spin wave propagation: in the backward volume geometry the band structure is conventional, while in the surface geometry the band structure is nonreciprocal and is formed by indirect band gaps. Placing a superconductor next to a ferromagnet makes it possible to modify the dispersion of spin waves. A ferromagnetic medium with a superconducting grid forms a magnonic crystal with allowed and forbidden frequency bands for spin wave propagation. The band structure of the crystal is shown to depend on the spin‐wave geometry as well as on the characteristics of superconducting microstructure.