Yttrium Iron Garnet Films Research Articles

Formirovanie polos nepropuskaniyaspin-volnovogo signala v meandrovykh strukturakh iz ZhIG

A meander waveguide made of an yttrium iron garnet (YIG) film with variation of the profile is studied with a view to the possible control of band bands for surface spin waves (SSWs). The finite element method is used to determine the control mechanism of forbidden band gaps in thin YIG films. The electromagnetic problem is solved, and the dispersion characteristics of spin waves are plotted for various geometrical parameters of the meander. The nature of the change in the frequency ranges of Bragg forbidden band gaps is studied in detail depending on the profile of the meander. It is demonstrated that a three-dimensional spin-wave structure with broken translational symmetry that uses vertical spin-wave transport provides an information signal transmission in a three-dimensional configuration of magnonic networks.

Upravlyaemaya lazernym izlucheniem spin-volnovaya interferentsiya v neregulyarnoy magnonnoy strukture

Using experimental and numerical investigation, we demonstrate laser-controlled propagation and interaction of spin waves in an irregular magnetic structure in the geometry of the Mach–Zehnder interferometer. It is shown that the use of laser radiation for heating one of the interferometer arms leads to controlled interference of a spin-wave signal in the output section. The yttrium–iron garnet film heating under the action of laser radiation is measured experimentally. Using micromagnetic modeling, the evolution of the spin-wave interference pattern under the action of laser heating of one of the interferometer arm is demonstrated. The results of this study ensure a simple solution for developing tunable spin-wave interferometers for the paradigm of the magnonic logics.

Интегрированные с ферритовым волноводом мультиэлектродные микроантены для возбуждения-приема спиновых волн

Multielectrode microantennas for spin waves integrated with a ferrite waveguide – yttrium iron garnet film – were fabricated and tested. Microantennas of two types were studied: with a parallel connection of conductors – “grating” and with a serial connection of conductors – “meander”. The performance of such microantennas for excitation of magnetostatic surface and backward volumec waves tens of micrometers in length has been demonstrated. It has been shown that for waves with a length of tens of micrometers, high (tens of megahertz) excitation selectivity can be achieved using the “grating” microantennas. Whereas, using the “meander” microantennas for the same wavelength range, it is possible not only to get selectivity, but also to significantly (up to 10 dB) increase the excitation efficiency compared to the microantenna with a single conductor. It is noted that the use of such microantennas for shorter spin waves can be hampered by the mutual influence of microwave fields from neighboring conductors, as well as the increasing role of ohmic losses in conductors.

Vacuum laser annealing of magnetooptical cerium-substituted yttrium iron garnet films

Laser annealing in a vacuum chamber was employed to achieve the selective crystallization of a cerium-substituted yttrium iron garnet (Ce:YIG, Ce1Y2Fe5O12) film on a glass substrate. The film was selectively crystallized using a continuous-wave laser, and the transmissivity, optical constants, electronic binding states, magnetic properties, and magnetooptical properties of the fabricated Ce:YIG films were measured. A single Ce:YIG phase was observed using X-ray diffraction, and the film's magnetization was comparable to that of Ce:YIG prepared by heater annealing. Faraday rotation angles of 0.50°/μm and −0.25°/μm were obtained at wavelengths of 532 nm and 1064 nm, respectively.

Спиновые волны в одномерных магнонных кристаллах с двумя пространственными периодами

The propagation of surface and backward volume magnetostatic waves in a one-dimensional magnonic crystal in the form of a yttrium iron garnet film with two periodic lattices of grooves with different periods etched on its surface was experimentally studied. It is shown that the form of the frequency dependence of the transmission coefficient of magnetostatic waves in such crystal is not a simple superposition of similar dependences for two magnonic crystals with the same lattice periods.

Correlation-Enhanced Interaction of a Bose-Einstein Condensate with Parametric Magnon Pairs and Virtual Magnons.

Nonlinear interactions are crucial in science and engineering. Here, we investigate wave interactions in a highly nonlinear magnetic system driven by parametric pumping leading to Bose-Einstein condensation of spin-wave quanta-magnons. Using Brillouin light scattering spectroscopy in yttrium-iron garnet films, we found and identified a set of nonlinear processes resulting in off-resonant spin-wave excitations-virtual magnons. In particular, we discovered a dynamically strong, correlation-enhanced four-wave interaction process of the magnon condensate with pairs of parametric magnons having opposite wave vectors and fully correlated phases.

Acoustic Coupling between Magnon Bose−Einstein Condensates in Yttrium Iron Garnet Films

Acoustic Coupling between Magnon Bose−Einstein Condensates in Yttrium Iron Garnet Films

Temperature controlled magnon–photon coupling in a YIG/GGG-superconducting cavity coupled system

To explore potential applications in classical and quantum information transfer, the hybrid systems between yttrium iron garnet (YIG) and cavities have been extensively studied, and four coupling regimes have been defined based on the relative strength between the coupling strength and dissipation rate of each subsystem. Achieving the control of magnon–photon coupling between nano-thick YIG films and cavities remains to be explored. We experimentally measure the microwave transmission spectra of a nano-thick yttrium iron garnet/gadolinium gallium garnet (YIG/GGG) film coupled to a superconducting cavity at different temperatures. The dissipation rate of the superconducting cavity increases significantly with decreasing temperature, which is influenced by the temperature-dependent magnetic susceptibility of the GGG substrate. Accompanied by the temperature-dependent magnon dissipation rate, a continuous transformation of the coupled system in strong coupling, Purcell and weak coupling regimes is achieved.

Rapid-prototyping of microscopic thermal landscapes in Brillouin light scattering spectroscopy.

Since temperature and its spatial, and temporal variations affect a wide range of physical properties of material systems, they can be used to create reconfigurable spatial structures of various types in physical and biological objects. This paper presents an experimental optical setup for creating tunable two-dimensional temperature patterns on a micrometer scale. As an example of its practical application, we have produced temperature-induced magnetization landscapes in ferrimagnetic yttrium iron garnet films and investigated them using micro-focused Brillouin light scattering spectroscopy. It is shown that, due to the temperature dependence of the magnon spectrum, spatial temperature distributions can be visualized even for microscale thermal patterns.

A spinwave Ising machine

Time-multiplexed Coherent Ising Machines (CIMs) have demonstrated promising results in rapidly solving large-scale combinatorial problems. However, CIMs remain relatively large and power-demanding. Here, we demonstrate a spinwave-based Ising machine (SWIM) that due to the low spinwave group velocity allows for sufficient miniaturization and reduced power consumption. The SWIM is implemented using a 10-mm-long 5-μm-thick Yttrium Iron Garnet film with off-the-shelf microwave components and can support an 8-spin MAX-CUT problem and solve it in less than 4 μs consuming only 7 μJ. As the SWIM minimizes its energy, we observe that the spin states can demonstrate both uniform and domain-propagation-like switching. The developed SWIM has the potential for substantial further miniaturization with reduction of power consumption, scalability in the number of supported spins, increase of operational speed, and may become a versatile platform for commercially feasible high-performance solvers of combinatorial optimization problems.

Chiral Excitation of Exchange Spin Waves Using Gold Nanowire Grating

We propose an experimental method for the unidirectional excitation of spin waves. By structuring Au nanowire arrays within a coplanar waveguide onto a thin yttrium iron garnet (YIG) film, we observe a chiral coupling between the excitation field geometry of the nanowire grating and several well-resolved propagating magnon modes. We report a propagating spin wave spectroscopy study with unprecedented spectral definition, wavelengths down to 130 nm and attenuation lengths well above 100 μm over the 20 GHz frequency band. The proposed experiment paves the way for future non-reciprocal magnonic devices.

Quantum information diode based on a magnonic crystal

Exploiting the effect of nonreciprocal magnons in a system with no inversion symmetry, we propose a concept of a quantum information diode (QID), i.e. a device rectifying the amount of quantum information transmitted in the opposite directions. We control the asymmetric left and right quantum information currents through an applied external electric field and quantify it through the left and right out-of-time-ordered correlation. To enhance the efficiency of the QID, we utilize a magnonic crystal. We excite magnons of different frequencies and let them propagate in opposite directions. Nonreciprocal magnons propagating in opposite directions have different dispersion relations. Magnons propagating in one direction match resonant conditions and scatter on gate magnons. Therefore, magnon flux in one direction is damped in the magnonic crystal leading to an asymmetric transport of quantum information in the QID. A QID can be fabricated from an yttrium iron garnet film. This is an experimentally feasible concept and implies certain conditions: low temperature and small deviation from the equilibrium to exclude effects of phonons and magnon interactions. We show that rectification of the flaw of quantum information can be controlled efficiently by an external electric field and magnetoelectric effects.

Broadband ferromagnetic resonance of ultrathin yttrium iron garnet films by pulsed laser deposition: Effects of deposition parameters

In this study, we investigate the growth and characteristics of ultrathin ferrimagnetic yttrium iron garnet (YIG, Y3Fe5O12) films on a Gallium Gadolinium Garnet (GGG) substrate using the pulsed laser deposition technique (PLD). We aim to improve the magnetic quality of the films by varying the deposition parameters, specifically the laser energy and oxygen pressure. We conduct broadband ferromagnetic resonance (FMR) measurements to characterize the magnetic properties and Gilbert damping of the films. Our findings demonstrate that adjusting the deposition parameters systematically controls the saturation magnetization and Gilbert damping of YIG films. Our measurements show that in the absence of oxygen, the films exhibit higher-than-expected values of magnetization and Gilbert damping, suggesting that the films have a higher Fe concentration. Conversely, when introducing oxygen in the chamber, we observe a decrease in the magnetization and damping values, approaching those of bulk YIG films. Notably, we achieve a saturation magnetization of 0.185 T and an ultra-low Gilbert damping of 1.7 ×10−4 for films deposited under conditions of high laser energy and oxygen pressure. This is mainly due to a better Y:Fe ratio approaching the stoichiometric value of 0.6 as the oxygen pressure increased. Our findings provide valuable insights for preparing high-quality ferrimagnetic films suitable for various magnonics applications and spin Hall devices.

Praseodymium-dopant effect on bismuth-substituted yttrium iron garnet films on fused silica glass substrate at the 1310 and 1550-nm wavelengths

The optical and magneto-optic (MO) properties of the praseodymium (Pr)-dopant effect on bismuth-substituted yttrium iron garnet (Bi:YIG) films coated on fused silica glass substrates by using the metal-organic-decomposition (MOD) method with chemical solutions were investigated at the 1310 and 1550-nm wavelength regions. The maximum Faraday rotation angle of the Pr-codoped Bi:YIG (Pr,By:YIG) film was observed to be 0.09 and 0.046 deg/μm at the wavelengths of 1310 and 1550 nm, respectively, when the film was annealed at a temperature of 750 °C, while those of the plain Bi:YIG film were 0.059 and 0.039 deg/μm. More than 50% improvement in the Faraday rotation value of the Pr,Bi:YIG film was observed compared to that of the Bi:YIG film at the 1310 nm wavelength. The absorption coefficient of the Pr,Bi:YIG film was comparable to that of the Bi:YIG film. Therefore, the Pr,Bi:YIG film prepared with the MOD method is potentially useful for MO applications such as optical isolators and circulators.

Nonlinear phase shifts induced by pumping spin waves in magnonic crystals

A nonlinear phase shift of low-power spin waves (SWs) induced by a high-power pumping SW excited both inside and outside the magnonic band-gaps of a magnonic crystal has been studied. The magnonic crystal with spatially periodic thickness is fabricated from an yttrium iron garnet film by chemical etching. The results show that the phase shift of the low-power SWs can be effectively controlled by variation of power level of the pumping SW. This induced nonlinear phase shift is weakened if the pump frequency lies in the magnonic bandgap. The data obtained are well explained by contradirectional coupling of the high-power forward and reflected spin waves. A theoretical model for this effect is presented. Our findings are important for the further progress in SW computing.

Propagating spin-wave spectroscopy in a liquid-phase epitaxial nanometer-thick YIG film at millikelvin temperatures

Performing propagating spin-wave spectroscopy of thin films at millikelvin temperatures is the next step toward the realization of large-scale integrated magnonic circuits for quantum applications. Here, we demonstrate spin-wave propagation in a 100 nm-thick yttrium-iron-garnet (YIG) film at temperatures down to 45 mK, using stripline nanoantennas deposited on YIG surface for electrical excitation and detection. The clear transmission characteristics over the distance of 10 μ m are measured and the extracted spin-wave group velocity and the YIG saturation magnetization agree well with the theoretical values. We show that the gadolinium-gallium-garnet (GGG) substrate influences the spin-wave propagation characteristics only for the applied magnetic fields beyond 75 mT, originating from a GGG magnetization up to 62 kA / m at 45 mK. Our results show that the developed fabrication and measurement methodologies enable the realization of integrated magnonic quantum nanotechnologies at millikelvin temperatures.

Nonlinear subswitching regime of magnetization dynamics in photomagnetic garnets

We analyze, both experimentally and numerically, the nonlinear regime of the photo-induced coherent magnetization dynamics in cobalt-doped yttrium iron garnet films. Photo-magnetic excitation with femtosecond laser pulses reveals a strongly nonlinear response of the spin subsystem with a significant increase of the effective Gilbert damping. By varying both laser fluence and the external magnetic field, we show that this nonlinearity originates in the anharmonicity of the magnetic energy landscape. We numerically map the parameter workspace for the nonlinear photo-induced spin dynamics below the photo-magnetic switching threshold. Corroborated by numerical simulations of the Landau-Lifshitz-Gilbert equation, our results highlight the key role of the cubic symmetry of the magnetic subsystem in reaching the nonlinear spin precession regime. These findings expand the fundamental understanding of laser-induced nonlinear spin dynamics as well as facilitate the development of applied photo-magnetism.

Control of spin wave propagation modes in the yttrium iron garnet waveguide by means of local laser heating

The results of micromagnetic modeling of the magnetic structure on the surface of a film of yttrium iron garnet (YIG) are presented, where a region of altered saturation magnetization was created by focused laser radiation. Based on the constructed amplitude-frequency characteristics of signal transmission through a magnon structure with a heating region, the possibility of implementing spin-wave signal filtering modes with a change in the diameter of the heated region on the YIG surface is shown.

Thermally induced all-optical ferromagnetic resonance in thin YIG films

All-optical ferromagnetic resonance (AO-FMR) is a powerful tool for the local detection of micromagnetic parameters, such as magnetic anisotropy, Gilbert damping or spin stiffness. In this work we demonstrate that the AO-FMR method can be used in thin films of yttrium iron garnet (YIG) if a metallic capping layer (Au, Pt) is deposited on top of the film. Magnetization precession is triggered by heating of the metallic layer with femtosecond laser pulses. The heat pulse modifies the magneto-crystalline anisotropy of the YIG film and shifts the quasi-equilibrium orientation of the magnetization, which results in precessional magnetization dynamics. The laser-induced magnetization precession corresponds to a uniform (Kittel) magnon mode, with the precession frequency determined by the magnetic anisotropy of the material as well as the external magnetic field, and the damping time set by a Gilbert damping parameter. The AO-FMR method thus enables measuring local magnetic properties, with a resolution given by the laser spot size.

All Acoustical Excitation of Spin Waves in High Overtone Bulk Acoustic Resonator

The hybrid high overtone bulk acoustic wave resonators (HBARs) consisting of a piezoelectric film transducers and gallium gadolinium garnet substrates with yttrium iron garnet films (YIG-GGG-YIG) are used for experimental excitation and detection of acoustically driven spin waves (ADSWs). Two types of HBAR transducers made of Al-ZnO-Al films (differed through the electrodes’ geometry) were deposited onto YIG-GGG-YIG trilayers with different YIG film thicknesses and doping levels and served for excitation of multimode HBAR at gigahertz frequencies. ADSWs were detected by measuring the shifts of resonant HBAR modes in a tangential external magnetic field when the conditions for magnetoelastic resonance (MER) were satisfied. It was shown that the design of the transducer with a continuous bottom electrode provides all acoustical excitation of spin waves (pure ADSWs), suppressing the additional inductive magnetic dynamics excitation due to the electrodes’ geometry. The theoretical study of the HBAR spectrum in a magnetic field showed that the resonance harmonics in the MER region can either almost continuously transfer from one to another, or decay and form an evident magnetoelastic gap. In this case, the shift of resonant frequencies can achieve several intermodal distances. The results obtained are important for applications of HBAR-based devices in spintronics and magnonics.