Ferromagnet/Superconductor Hybrid Magnonic Metamaterials.

Igor A Golovchanskiy,Pavel S Dzhumaev,Olga V Emelyanova,Vasily S Stolyarov,Nikolay N Abramov,Valery V Ryazanov,Alexander A Golubov,Alexey V Ustinov

doi:10.1002/advs.201900435

Abstract

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.

Highlights

Summarizing, in this work we have considered magnetization dynamics in ferromagnet/superconductor hybrid magnonic crystals (MCs), which consist of a ferromagnetic film coupled inductively to a superconducting periodic microstructure
Studying the ferromagnetic resonance (FMR) spectrum of the hybrid, we have defined the actual contribution of the superconducting periodic subsystem to magnetization dynamics, that is the diamagnetic response of the superconductor
We have observed the correlation of the FMR spectrum with the superconducting critical states, have identified the Meissner state and the vortex-penetrated state

Summary

Introduction

Ustinov National University of Science and Technology MISIS 4 Leninsky prosp., 119049 Moscow, Russia. Ryazanov Institute of Solid State Physics (ISSP RAS) Chernogolovka 142432, Moscow Region, Russia. Ryazanov Faculty of Physics National Research University Higher School of Economics 21/4 Staraya Basmannaya Str., 105066 Moscow, Russia. A rich variety of approaches exists for development of 1D and 2D MCs in planar geometry. This variety includes straightforward ways, such as periodic grooving or thinning of ferromagnetic films,[18,19,20] as well as more sophisticated techniques. We propose to employ capabilities of superconductors to modify dynamic properties of ferromagnets for development of a medium with periodically modulated spin wave dispersion. Development of MCs by hybridizing ferromagnetic films with superconductors may appear to be effective for application in cryogenic temperatures (see references in ref. [32]), it paves the way for design of tunable MCs on microscales

Results and Discussions

FMR Spectrum of Hybrid Metamaterials

Magnonic Band Structures of Hybrid Metamaterials

Conclusion

Experimental Section

Conflict of Interest