Low-loss YIG-based magnonic crystals with large tunable bandgaps

Abstract

Control of spin waves in magnonic crystals is essential for magnon-based computing. Crystals made of ferromagnetic metals offer versatility in band structure design, but strong magnetic damping restricts their transmission efficiency. Yttrium iron garnet (YIG) with ultralow damping is the palpable alternative, yet its small saturation magnetization limits dipolar coupling between discrete units. Here, we experimentally demonstrate low-loss spin-wave manipulation in magnonic crystals of physically separated nanometer-thick YIG stripes. We enhance the transmission of spin waves in allowed minibands by filling the gaps between YIG stripes with CoFeB. Thus-formed magnonic crystals exhibit tunable bandgaps of 50–200 MHz with nearly complete suppression of the spin-wave signal. We also show that Bragg scattering on only two units produces clear frequency gaps in spin-wave transmission spectra. The integration of strong ferromagnets in nanometer-thick YIG-based magnonic crystals provides effective spin-wave manipulation and low-loss propagation, a vital parameter combination for magnonic technologies.

Nanometer-thick YIG-based magnonic crystals: Bandgap dependence on groove depth, lattice constant, and film thickness

“…Recently, we demonstrated the formation of bandgaps with sizes up to 200 MHz in lattices comprising only a few discrete 260-nm-thick YIG stripes. 35 The YIG stripes in this study were separated by either air grooves or grooves that were filled with CoFeB. Compared to micrometer-thick YIG films, the opening of larger bandgaps with fewer lattice units in thin discrete YIG-based crystals is explained by stronger Bragg reflection on individual scatterers.…”

“…20 Programmable control of spin-wave transmission in micrometer-thick YIG films has been demonstrated using currentcarrying meander structures, 21,22 optical absorbers, 23 and strain coupling to a piezoelectric layer. 24 Following advances in the growth of nanometer-thick YIG films with ultralow magnetic damping, [25][26][27][28][29][30][31] the excitation and low-loss propagation of short-wavelength spin waves [32][33][34] and downscaling of YIG-based magnonic crystals 35 are now possible. Recently, we demonstrated the formation of bandgaps with sizes up to 200 MHz in lattices comprising only a few discrete 260-nm-thick YIG stripes.…”

Quantum Spin-Wave Materials, Interface Effects and Functional Devices for Information Applications

“…Spin waves usually propagate in the waveguides made of magnetic thin films or strips. The spin-wave dispersion (the relationship between the spin-wave frequency f and the wave number k) depends on various parameters, such as the waveguide geometry (Chumak et al, 2014), Oersted field induced by the electric current (Rousseau et al, 2015) and spin-wave material properties (Qin et al, 2018), etc. Among these parameters, the magnetic material determines the basic performance of the device.…”

Parametric Generation of Propagating Spin Waves in Ultrathin Yttrium Iron Garnet Waveguides

“…The field of nano‐YIG magnonics is growing very rapidly; however, the knowledge of parametric generation of SWs in these systems is still lacking. Here, we present experimental demonstration of the parametric generation of propagating SWs in a nanometer‐thick YIG waveguide (WG).…”