Demonstration of a robust magnonic spin wave interferometer

Abstract

Magnonics is an emerging field dealing with ultralow power consumption logic circuits, in which the flow of spin waves, rather than electric charges, transmits and processes information. Waves, including spin waves, excel at encoding information via their phase using interference. This enables a number of inputs to be processed in one device, which offers the promise of multi-input multi-output logic gates. To realize such an integrated device, it is essential to demonstrate spin wave interferometers using spatially isotropic spin waves with high operational stability. However, spin wave reflection at the waveguide edge has previously limited the stability of interfering waves, precluding the use of isotropic spin waves, i.e., forward volume waves. Here, a spin wave absorber is demonstrated comprising a yttrium iron garnet waveguide partially covered by gold. This device is shown experimentally to be a robust spin wave interferometer using the forward volume mode, with a large ON/OFF isolation value of 13.7 dB even in magnetic fields over 30 Oe.A spin wave (SW) is a radio frequency (rf) collective excitation of the magnetic moments in a magnetic material, a magnetic counterpart of elastic waves. The transmission properties of SWs can be extensively modulated depending on the strength of the bias magnetic field, the waveguide material and the geometry 1,2 . This enables engineering of arbitrary band structures for carrier signals in the several-GHz range. These unique properties have been widely used to design passive radio frequency elements, including tunable filters 3 and delay lines 4 . However, the most important feature of SWs is their propagation without charge transport. Thus SWs have attracted attention because they offer a new paradigm for information processing in which Joule loss and its accompanying heat generation is expected to be extremely small. Therefore, SWs could be used to represent information in beyond-CMOS devices 5 . To develop logic circuits based on SWs, active control of SW flow is required. Recently, a variety of systems showing spin dynamic effects 6-12 and artificially designed structures [13][14][15][16][17][18] manipulating the local magnetic moments have been investigated. These novel systems have motivated the creation of magnonics as a research field that addresses transport, storage and processing information using SWs 19,20 . A significant feature of SWs compared to other information carriers is the usefulness of their phase information, which can be easily manipulated in logic operations. Therefore a SW interferometer is an essential component for realization of logic devices [21][22][23] . Yttrium iron garnet (YIG) is suitable for SW waveguides because of its low magnetic damping and low out-of-plane saturation magnetic field [24][25][26][27][28] . Magnons can therefore conserve their phase information over long distances in a YIG waveguide. Yu et al. recently experimentally observed SW propagation over 600 μm using a 20 nm-thick YIG waveguide with in-plane magnetization 29...

One-Dimensional Magnonic Crystal With Cu Stripes for Forward Volume Spin Waves

“…As shown in Ref. [39], the wavenumber k Cu−YIG of the FV SW propagation in Cu-YIG is twice that in bare k YIG (= k). Thus, at f = 1.8 GHz, the calculated wavenumbers are k YIG = 3.7578 mm −1 (λ YIG = 1.672 mm) and k Cu−YIG = 1.8789 mm −1 (λ Cu−YIG = 3.344 mm), respectively.…”

“…We employ metallization techniques to modulate the wavelength of the FV SW for realizing MCs [18,19,30,39,44,45]. As shown in Ref.…”

“…The lattice constant is 1.254 mm. The edges of the YIG waveguide outside the MSLs are covered by 30-nm-thick Au films, which function as SW absorbers for suppressing edge reflections and spectral noise [22,39,40,46]. The length of the Au L Au−YIG is 1.8 mm, the distance between the edges of the Au film and the edges of the MSL is 0.2 mm, the conductivity of the Au is 4.56 × 10 7 S/m, and the position and thickness of the SW absorbers are as discussed and specified in Ref.…”

“…This is mainly because of the significant noise in the FV SW configuration, which makes it difficult to observe a magnonic band gap (MBG) in experiments that employ low damping materials (yttrium iron garnets, YIG) as waveguides. In this study, we demonstrate a 1D MC for FV SW propagation in YIG film by introducing a noise suppression technique based on metallization [22,39,40]. The radio frequency (rf) powers used for exciting SWs in this study are in the linear region, and the SWs are dipolar SWs because the wavenumber is in the order of mm [8].…”

Static and Dynamic Magnetic Properties of Single‐Crystalline Yttrium Iron Garnet Films Epitaxially Grown on Three Garnet Substrates

“…Yttrium iron garnet (YIG) is extensively used for SW devices [11][12][13] because of its low intrinsic Gilbert damping, [14][15][16][17][18][19] but other materials with low Gilbert damping have been proposed, including Permalloy [20,21] and Heusler alloys. Yttrium iron garnet (YIG) is extensively used for SW devices [11][12][13] because of its low intrinsic Gilbert damping, [14][15][16][17][18][19] but other materials with low Gilbert damping have been proposed, including Permalloy [20,21] and Heusler alloys.…”