arXiv subjects

Andrey A. Voronov

Publications and source records attributed to Andrey A. Voronov.

8 recordsLinked to original sources

arXiv2025

k-Selective Electrical-to-Magnon Transduction with Realistic Field-distributed Nanoantennas

The excitation and detection of propagating spin waves with lithographed nanoantennas underpin both classical magnonic circuits and emerging quantum technologies. Here, we establish a framework for all-electrical propagating spin-wave spectroscopy (AEPSWS) that links realistic electromagnetic drive fields to micromagnetic dynamics. Using finite-element (FE) simulations, we compute the full vector near-field of electrical impedance-matched, tapered coplanar and stripline antennas and import this distribution into finite-difference (FD) micromagnetic solvers. This approach captures the antenna-limited wave-vector spectrum and the component-selective driving fields (perpendicular to the static magnetisation) that simplified uniform-field models cannot. From this coupling, we derive how realistic current return paths and tapering shapes, k-weighting functions, for Damon-Eshbach surface spin waves in yttrium-iron-garnet (YIG) films are, for millimetre-scale matched CPWs and linear tapers down to nanometre-scale antennas. Validation against experimental AEPSWS on a $48\,nm$ YIG film shows quantitative agreement in dispersion ridges, group velocities, and spectral peak positions, establishing that the antenna acts as a tunable k-space filter. These results provide actionable design rules for on-chip magnonic transducers, with immediate relevance for low-power operation regimes and prospective applications in quantum magnonics.

cond-mat.mes-hall↗

arXiv2025

Exchange spin-wave propagation in Ga:YIG nanowaveguides

Spin-wave-based computing has emerged as a promising approach to overcome the fundamental limitations of CMOS technologies. However, the increasing demand for device miniaturization down to a 100 nm scale presents significant challenges for long-distance spin-wave transport. Gallium-substituted yttrium iron garnet (Ga:YIG) offers a potential solution to these challenges due to its unique magnetic properties. The reduced saturation magnetization in Ga:YIG enables efficient excitation of exchange-dominated spin waves, which exhibit enhanced transport characteristics compared to dipolar-dominated modes in conventional materials. Here, we present the first comprehensive study combining experimental, analytical, and numerical investigations of spin-wave propagation in Ga:YIG waveguides down to 145 nm width and 73 nm thickness. Using micro-focused Brillouin light scattering spectroscopy, TetraX simulations, and analytical dispersion calculations, we demonstrate that Ga:YIG waveguides support spin waves with significantly higher group velocities up to 600 m/s. This value remains constant for structures with different widths, leading to longer spin-wave propagation lengths in nanowaveguides compared to non-substituted YIG. These results reveal that gallium substitution provides access to faster and longer-lived spin waves, opening new possibilities for implementing this material in nanoscale magnonic devices.

cond-mat.other↗

arXiv2025

Inverse-design topology optimization of magnonic devices using level-set method

The inverse design approach in magnonics exploits the wave nature of magnons and machine learning to develop logical devices with functionalities that exceed the capabilities of analytical methods. While promising for analog, Boolean, and neuromorphic computing, current implementations face memory limitations that hinder the design of complex systems. This study presents a level-set parameterization method for topology optimization, combined with an adjoint-state approach for memory-efficient simulation of magnetization dynamics. The framework is implemented in NeuralMag, a GPU-accelerated micromagnetic solver featuring a nodal finite-difference scheme and automatic differentiation tools. To validate the method, we optimized the shape of a magnetic nanoparticle by applying constraints to the objective function, and designed a 300-nm-wide yttrium iron garnet demultiplexer achieving frequency-selective spin-wave separation. These results highlight the algorithm's efficiency in exploring local minima across various initial configurations, establishing its utility as a versatile tool for the inverse design of magnonic logic devices.

cond-mat.other↗

arXiv2025

Elimination of substrate-induced FMR linewidth broadening in the epitaxial system YIG-GGG by microstructuring

Modern quantum technologies and hybrid quantum systems offer the opportunity to utilize magnons on the level of single excitations. Long lifetimes, low decoherence rates, and a strong coupling rate to other subsystems propose the ferrimagnet yttrium iron garnet (YIG), grown on a gadolinium gallium garnet (GGG) substrate, as a suitable platform to host magnonic quantum states. However, the magnetic damping at cryogenic temperatures significantly increases due to the paramagnetic character and the highly inhomogeneous stray field of GGG, as recent experiments and simulations pointed out. Here, we report on temperature dependent ferromagnetic resonance (FMR) spectroscopy studies in YIG-GGG thin-films with different sample geometries. We experimentally demonstrate how to eliminate the asymmetric stray field-induced linewidth broadening via microstructuring of the YIG film. Additionally, our experiments reveal evidence of a non-Gilbert like behavior of the linewidth at cryogenic temperatures, independent of the inhomogeneous GGG stray field.

cond-mat.mes-hall↗

arXiv2024

Damping Enhancement in YIG at Millikelvin Temperatures due to GGG Substrate

Quantum magnonics aims to exploit the quantum mechanical properties of magnons for nanoscale quantum information technologies. Ferrimagnetic yttrium iron garnet (YIG), which offers the longest magnon lifetimes, is a key material typically grown on gadolinium gallium garnet (GGG) substrates for structural compatibility. However, the increased magnetic damping in YIG/GGG systems below 50$\,$K poses a challenge for quantum applications. Here, we study the damping in a 97$\,$nm-thick YIG film on a 500$\,μ$m-thick GGG substrate at temperatures down to 30$\,$mK using ferromagnetic resonance (FMR) spectroscopy. We show that the dominant physical mechanism for the observed tenfold increase in FMR linewidth at millikelvin temperatures is the non-uniform bias magnetic field generated by the partially magnetized paramagnetic GGG substrate. Numerical simulations and analytical theory show that the GGG-driven linewidth enhancement can reach up to 6.7 times. In addition, at low temperatures and frequencies above 18$\,$GHz, the FMR linewidth deviates from the viscous Gilbert-damping model. These results allow the partial elimination of the damping mechanisms attributed to GGG, which is necessary for the advancement of solid-state quantum technologies.

cond-mat.mes-hall↗

arXiv2024

Wavenumber-dependent magnetic losses in YIG-GGG heterostructures at millikelvin temperatures

Magnons have inspired potential applications in modern quantum technologies and hybrid quantum systems due to their intrinsic nonlinearity, nanoscale scalability, and a unique set of experimentally accessible parameters for manipulating their dispersion. Such magnon-based quantum technologies demand long decoherence times, millikelvin temperatures, and minimal dissipation. Due to its low magnetic damping, the ferrimagnet yttrium iron garnet (YIG), grown on gadolinium gallium garnet (GGG), is the most promising material for this objective. To comprehend the magnetic losses of propagating magnons in such YIG-GGG heterostructures at cryogenic temperatures, we investigate magnon transport in a micrometer-thick YIG sample via propagating spin-wave spectroscopy (PSWS) measurements for temperatures between 4K to 26mK. We demonstrate an increase in the dissipation rate with wavenumber at cryogenic temperatures, caused by dipolar coupling to the partially magnetized GGG substrate. Additionally, we observe a temperature-dependent decrease in spin-wave transmission, attributed to rare earth ion relaxations. The critical role of the additional dissipation channels at cryogenic temperatures is underpinned by the comparison of the experimental results with theoretical calculations and micromagnetic simulations. Our findings strengthen the understanding of magnon losses at millikelvin temperatures, which is essential for the future detection of individual propagating magnons.

cond-mat.mes-hall↗

arXiv2024

Magnetic anisotropy and GGG substrate stray field in YIG films down to millikelvin temperatures

Quantum magnonics investigates the quantum-mechanical properties of magnons such as quantum coherence or entanglement for solid-state quantum information technologies at the nanoscale. The most promising material for quantum magnonics is the ferrimagnetic yttrium iron garnet (YIG), which hosts magnons with the longest lifetimes. YIG films of the highest quality are grown on a paramagnetic gadolinium gallium garnet (GGG) substrate. The literature has reported that ferromagnetic resonance (FMR) frequencies of YIG/GGG decrease at temperatures below 50 K despite the increase in YIG magnetization. We investigated a 97 nm-thick YIG film grown on 500 $\mathrmμ$m-thick GGG substrate through a series of experiments conducted at temperatures as low as 30 mK, and using both analytical and numerical methods. Our findings suggest that the primary factor contributing to the FMR frequency shift is the stray magnetic field created by the partially magnetized GGG substrate. This stray field is antiparallel to the applied external field and is highly inhomogeneous, reaching up to 40 mT in the center of the sample. At temperatures below 500 mK, the GGG field exhibits a saturation that cannot be described by the standard Brillouin function for a paramagnet. Including the calculated GGG field in the analysis of the FMR frequency versus temperature dependence allowed the determination of the cubic and uniaxial anisotropies. We find that the total anisotropy increases more than three times with the decrease in temperature down to 2 K. Our findings enable accurate predictions of the YIG/GGG magnetic systems behavior at low and ultra-low millikelvin temperatures, crucial for developing quantum magnonic devices.

cond-mat.mes-hall↗

arXiv2021

Magneto-optics of the 2D iron-garnet nanocylinder array with localized and lattice modes

We experimentally show the enhancement of the Faraday and transverse magneto-optical Kerr effects in the two-dimensional arrays of nanocylinders made of bismuth-substituted iron-garnet and supporting both localized and lattice modes. Simultaneous excitation of these modes makes it possible to increase the Faraday rotation by 3 times and TMOKE by an order of magnitude compared to the smooth magnetic film of the equal effective thickness. Both magneto-optical effects are enhanced in wide spectral and angular ranges making the nanocylinder array magnetic dielectric structures promising for applications with short and tightly-focused laser pulses.

physics.optics↗