arXiv subjects

G. Schmidt

Publications and source records attributed to G. Schmidt.

At least 19 recordsLinked to original sources

arXiv2026

Detection and characterisation of binary asteroid candidates through stellar occultations

Binary asteroids provide key access to fundamental parameters of Solar System remnants and planetary formations. However, the current knowledge of binary asteroids remains strongly biased by observational limitations, and main belt binary systems are still poorly characterised since current techniques preferentially detect either widely separated binaries close and bright systems. In this context, the high-precision astrometry of the Gaia mission has revealed a new population of candidate binaries exhibiting dynamical signatures consistent with unresolved companions. This work is part of the GaiaMoons program, and our aim with it was to characterise a sample of 357 potential binary asteroid targets and confirm or refute their binary nature. The properties of these candidates were derived from the high-precision photometric and astrometric observations provided by Gaia. We adopted stellar occultation as the observational method to study these targets. Between October 2023 and February 2026, we successfully carried out 165 observations for 101 targets. We subsequently analysed these events in the context of the available literature and previously reported observations. Thirty three observation led at least two positives for 24 objects that have undergone unprecedented occultation observation campaigns, with four objects showing indications of binary or contact binary features, namely 1127 Mimi, 35420 1998 AG6, 206 Hersilia, and 36882 2000 SW155. For the vast majority of these objects, the resulting dataset from all reduced observations provides unique physical and astrometric constraints, as they had never been observed through stellar occultations before. GaiaMoons illustrates how stellar occultation campaigns associated with Gaia observations generate a self-improving cycle to find new binary, thereby probing size and shape to constrain future observations.

astro-ph.EP↗

arXiv2026

Thin-Film-Engineered Self-Assembly of 3D Coaxial Microfluidics with a Tunable Polyimide Membrane for Bioelectronic Power

Thin-film self-assembly of three-dimensional (3D) microsystems presents a compelling route to integrate complex functionalities into ultra-compact volumes, yet strategies for incorporating tunable ion-conducting elements remain limited. Here, we introduce a strain-induced self assembly platform that transforms lithographically patterned multilayer thin films into functional 3D coaxial Swiss-roll microtubes with total active volumes below 1 uL. A key innovation is the monolithic integration of a chemically tunable polyimide proton-exchange membrane, enabling post-fabrication optimization of ionic transport that balances proton transport with mediator blocking. We further implement a dual-mode operational scheme that decouples microbial metabolism from electrochemical power generation, revealing biofouling, not chemical fouling or membrane degradation, as the dominant failure mechanism in conventional architectures. Critically, optimally treated polyimide membranes exhibit excellent recoverability after fouling, while cell-free mode operation maintains stable performance by physically excluding microorganisms from the microelectronic environment. This integrated bio-electronic microsystem achieves a volumetric power density of ~3.1 mW cm-3 within an ultra-compact footprint of 4.16 mm2. Our work establishes a scalable thin-film engineering approach to create tunable, 3D bioelectronic power sources for autonomous microsystems.

physics.app-ph↗

arXiv2025

Highly efficient coherent amplification of zero-field spin waves in YIG nano-waveguides

Transmission and processing of information at the nanoscale using spin waves and their quanta - magnons, offers numerous advantages and opportunities that make it a promising next-generation technology for integrated electronics. The main challenges that still need to be addressed to ensure high competitiveness of magnonic devices include finding ways to efficiently amplify spin waves in nanostructures and developing nanocircuits that can operate without the need for an external bias magnetic field. Here we demonstrate how these two challenges can be solved using nano-waveguides fabricated from a low-loss magnetic insulator. We show that by using local parametric pumping with a power of only a few milliwatts, one can achieve coherent amplification of spin-wave pulses by more than two orders of magnitude at zero bias magnetic field. Our results provide a simple solution to problems that have long prevented the implementation of efficient integrated magnonic circuits.

cond-mat.mes-hall↗

arXiv2025

Resonant inter-mode second harmonic generation by backward spin waves in YIG nano-waveguides

We experimentally study nonlinear generation of the second harmonic by backward volume spin waves propagating in microscopic magnonic waveguides fabricated from a low-loss magnetic insulator with a thickness of several tens of nanometers. We show that highly efficient resonant second harmonic generation is possible in the inter-mode regime at microwave powers of the order of 10^-4 W. In contrast to previously observed second harmonic generation processes, the generation by backward waves is characterized by the nonlinearly generated waves propagating opposite to the initial waves, and can be realized at zero bias magnetic field.

cond-mat.mes-hall↗

arXiv2024

Spatially-extended nonlinear generation of short-wavelength spin waves in YIG nanowaveguides

We experimentally study nonlinear propagation of spin waves in microscopic yttrium iron garnet waveguides, where the dispersion spectrum is engineered to enable efficient four-magnon interactions over a wide range of wavelengths. We show that under these conditions, the initial monochromatic spin wave nonlinearly generates co-propagating spin waves with well-defined, discrete frequencies. This process is characterized by a low energy threshold and can be observed in a wide range of frequencies and excitation powers. Thanks to the engineered dispersion, the process allows the generation of waves with short wavelengths that cannot be excited directly by a linear excitation mechanism. The nonlinearly generated short-wavelength spin waves continuously acquire the energy from the initial pump wave during co-propagation, which results in compensation of their propagation losses over significant distances. The observed phenomena can be used to implement frequency- and wavelength-conversion operations in magnonic nanodevices and circuits.

cond-mat.mes-hall↗

arXiv2024

Resonant generation of propagating second-harmonic spin waves in nano-waveguides

Generation of second-harmonic waves is one of the universal nonlinear phenomena that have found numerous technical applications in many modern technologies, in particular, in photonics. This phenomenon also has great potential in the field of magnonics, which considers the use of spin waves in magnetic nanostructures to implement wave-based signal processing and computing. However, due to the strong frequency dependence of the phase velocity of spin waves, resonant phase-matched generation of second-harmonic spin waves has not yet been achieved in practice. Here, we show experimentally that such a process can be realized using a combination of different modes of nano-sized spin-wave waveguides based on low-damping magnetic insulators. We demonstrate that our approach enables efficient spatially-extended energy transfer between interacting waves, which can be controlled by the intensity of the initial wave and the static magnetic field. The demonstrated approach can be used for the generation of short-wavelength spin waves that are difficult to excite directly, as well as for the implementation of novel devices for magnonic logic and unconventional computing.

cond-mat.mes-hall↗

arXiv2024

Laser patterning of magnonic structure via local crystallization of Yittrium Iron Garnet

The fabrication and integration of high-quality structures of Yttrium Iron Garnet (YIG) is critical for magnonics.Films with excellent properties are obtained only on single crystal Gadolinium Gallium Garnet (GGG) substrates using high-temperature processes. The subsequent realization of magnonic structures via lithography and etching is not straightforward as it requires a tight control of the edge roughness, to avoid magnon scattering, and planarization in case of multilayer devices. In this work we describe a different approach based on local laser annealing of amorphous YIG films, avoiding the need for subjecting the entire sample to high thermal budgets and for physical etching. Starting from amorphous and paramagnetic YIG films grown by pulsed laser deposition at room temperature on GGG, a 405 nm laser is used for patterning arbitrary shaped ferrimagnetic structures by local crystallization. In thick films (160 nm) the laser induced surface corrugation prevents the propagation of spin-wave modes in patterned conduits. For thinner films (80 nm) coherent propagation is observed in 1.2 micron wide conduits displaying an attenuation length of 5 micron which is compatible with a damping coefficient of about 5e-3. Possible routes to achieve damping coefficients compatible with state-of-the art epitaxial YIG films are discussed.

physics.app-ph↗

arXiv2023

Low Noise Inverse Magnetoelectric Magnetic Field Sensor

In the development of any type of magnetic field sensor based on magnetic films, special consideration must be given to the magnetic layer component. The presented work investigates the use of flux closing magnetostrictive multilayers for inverse magnetoelectric sensors. In such a type of magnetic field sensor, highly sensitive AC and DC field detection relies on strong excitation of the incorporated magnetic layers by piezoelectrically driven cantilever oscillation at mechanical resonances. The provoked periodic flux change is influenced by the magnetic field to be measured and is picked up by a coil, which generates the measured output. The effect of the magnetic multilayer on linearity, noise behavior, and detection limit of DC and AC signals is investigated. This study demonstrates the next step for inverse magnetoelectric thin film sensors, which achieve one order of magnitude improved detection limits with less than $8 pT/Hz^{1/2}$ at $10 Hz$ and $18 pT/Hz^{1/2}$ at $DC$ using exchange bias stabilized magnetic multilayers for obtaining flux closure.

eess.SP↗

arXiv2023

Zero-field spin waves in YIG nano-waveguides

Spin-wave based transmission and processing of information is a promising emerging nano-technology that can help overcome limitations of traditional electronics based on the transfer of electrical charge. Among the most important challenges for this technology is the implementation of spin-wave devices that can operate without the need for an external bias magnetic field. Here we experimentally demonstrate that this can be achieved using sub-micrometer wide spin-wave waveguides fabricated from ultrathin films of low-loss magnetic insulator - Yttrium Iron Garnet (YIG). We show that these waveguides exhibit a highly stable single-domain static magnetic configuration at zero field and support long-range propagation of spin waves with gigahertz frequencies. The experimental results are supported by micromagnetic simulations, which additionally provide information for optimization of zero-field guiding structures. Our findings create the basis for the development of energy-efficient zero-field spin-wave devices and circuits.

cond-mat.mes-hall↗

arXiv2022

Interplay between nonlinear spectral shift and nonlinear damping of spin waves in ultrathin YIG waveguides

We use the phase-resolved imaging to directly study the nonlinear modification of the wavelength of spin waves propagating in 100-nm thick, in-plane magnetized YIG waveguides. We show that, by using moderate microwave powers, one can realize spin waves with large amplitudes corresponding to precession angles in excess of 10 degrees and nonlinear wavelength variation of up to 18 percent in this system. We also find that, at large precession angles, the propagation of spin waves is strongly affected by the onset of nonlinear damping, which results in a strong spatial dependence of the wavelength. This effect leads to a spatially dependent controllability of the wavelength by the microwave power. Furthermore, it leads to the saturation of nonlinear spectral shift's effects several micrometers away from the excitation point. These findings are important for the development of nonlinear, integrated spin-wave signal processing devices and can be used to optimize their characteristics.

cond-mat.mes-hall↗

arXiv2021

Efficient geometrical control of spin waves in microscopic YIG waveguides

We study experimentally and by micromagnetic simulations the propagation of spin waves in 100-nm thick YIG waveguides, where the width linearly decreases from 2 to 0.5 micrometers over a transition region with varying length between 2.5 and 10 micrometers. We show that this geometry results in a down-conversion of the wavelength, enabling efficient generation of waves with wavelengths down to 350 nm. We also find that this geometry leads to a modification of the group velocity, allowing for almost-dispersionless propagation of spin-wave pulses. Moreover, we demonstrate that the influence of energy concentration outweighs that of damping in these YIG waveguides, resulting in an overall increase of the spin-wave intensity during propagation in the transition region. These findings can be utilized to improve the efficiency and functionality of magnonic devices which use spin waves as an information carrier.

cond-mat.mes-hall↗

arXiv2021

Roadmap on Spin-Wave Computing

Magnonics is a field of science that addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operations in the GHz-to-THz frequency range, utilization of nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors that covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with Boolean digital data, unconventional approaches like neuromorphic computing, and the progress towards magnon-based quantum computing. The article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of the current challenges and the outlook of the further development of the research directions.

physics.app-ph↗

arXiv2021

Anisotropic magnetotransport in LaAlO$_3$/SrTiO$_3$ nanostructures

A number of recent studies indicate that the charge conduction of the LaAlO$_3$/SrTiO$_3$ interface at low temperature is confined to filaments which are linked to structural domain walls in the SrTiO$_3$ with drastic consequences for example for the temperature dependence of local transport properties. We demonstrate that as a consequences of this current carrying filaments on the nano-scale the magnetotransport properties of the interface are highly anisotropic. Our magnetoresistance measurements reveal that the magnetoresistance in different nanostructures ($<500nm$) is random in magnitude and sign, respectively. Warming up nanostructures above the structural phase transition temperature (105K) results in the significant change in MR. Even a sign change of the magnetoresistance is possible. The results suggest that domain walls that are differently oriented with respect to the surface exhibit different respective magnetoresistance and the total magnetoresistance is a result of a random domain wall pattern formed during the structural phase transition in the SrTiO$_3$ at cool down.

cond-mat.mes-hall↗

arXiv2020

Integration and characterization of micron-sized YIG structures with very low Gilbert damping on arbitrary substrates

We present a novel process that allows the transfer of monocrystalline yttrium-iron-garnet microstructures onto virtually any kind of substrate. The process is based on a recently developed method that allows the fabrication of freestanding monocrystalline YIG bridges on gadolinium-gallium-garnet. Here the bridges' spans are detached from the substrate by a dry etching process and immersed in a watery solution. Using drop casting the immersed YIG platelets can be transferred onto the substrate of choice, where the structures finally can be reattached and thus be integrated into complex devices or experimental geometries. Using time resolved scanning Kerr microscopy and inductively measured ferromagnetic resonance we can demonstrate that the structures retain their excellent magnetic quality. At room temperature we find a ferromagnetic resonance linewidth of $μ_0ΔH_{HWHM}\approx 195\,μT$ and we were even able to inductively measure magnon spectra on a single micron-sized yttrium-iron-garnet platelet at a temperature of 5 K. The process is flexible in terms of substrate material and shape of the structure. In the future this approach will allow for new types of spin dynamics experiments up to now unthinkable.

cond-mat.mes-hall↗

arXiv2020

Ultra Thin Films of Yttrium Iron Garnet with Very Low Damping: A Review

Thin Yttrium Iron Garnet (YIG) is a promising material for integrated magnonics. In order to introduce YIG into nanofabrication processes it is necessary to fabricate very thin YIG films with a thickness well below 100 nm while retaining the extraordinary magnetic properties of the material, especially its long magnon lifetime and spin wave propagation length. Here, we give a brief introduction into the topic and we review and discuss the various results published over the last decade in this area. Especially for ultrathin films it turns out that pulsed layer deposition and sputtering are the most promising candidates. In addition, we discuss the application of room temperature deposition and annealing for lift-off based nanopatterning and the properties of nanostructures obtained by this method over the past years.

cond-mat.mtrl-sci↗

arXiv2019

Present criteria for prophylactic ICD implantation: Insights from the EU-CERT-ICD (Comparative Effectiveness Research to Assess the Use of Primary ProphylacTic Implantable Cardioverter Defibrillators in EUrope) project

BACKGROUND. The clinical effectiveness of primary prevention implantable cardioverter defibrillator (ICD) therapy is under debate. It is urgently needed to better identify patients who benefit from prophylactic ICD therapy. The EUropean Comparative Effectiveness Research to Assess the Use of Primary ProphylacTic Implantable Cardioverter Defibrillators (EU-CERT-ICD) completed in 2019 will assess this issue. SUMMARY. The EU-CERT-ICD is a prospective investigator-initiated non-randomized, controlled, multicenter observational cohort study done in 44 centers across 15 European countries. A total of 2327 patients with heart failure due to ischemic heart disease or dilated cardiomyopathy indicated for primary prophylactic ICD implantation were recruited between 2014 and 2018 (>1500 patients at first ICD implantation, >750 patients non-randomized non-ICD control group). The primary endpoint was all-cause mortality, first appropriate shock was co-primary endpoint. At baseline, all patients underwent 12-lead ECG and Holter-ECG analysis using multiple advanced methods for risk stratification as well as documentation of clinical characteristics and laboratory values. The EU-CERT-ICD data will provide much needed information on the survival benefit of preventive ICD therapy and expand on previous prospective risk stratification studies which showed very good applicability of clinical parameters and advanced risk stratifiers in order to define patient subgroups with above or below average ICD benefit. CONCLUSION. The EU-CERT-ICD study will provide new and current data about effectiveness of primary prophylactic ICD implantation. The study also aims for improved risk stratification and patient selection using clinical risk markers in general, and advanced ECG risk markers in particular.

stat.AP↗

arXiv2019

Nanoscale tunnel field effect transistor based on a complex oxide lateral heterostructure

We demonstrate a tunnel field effect transistor based on a lateral heterostructure patterned from an $\mathrm{LaAlO_3/SrTiO_3}$ electron gas. Charge is injected by tunneling from the $\mathrm{LaAlO_3}$/$\mathrm{SrTiO_3}$ contacts and the current through a narrow channel of insulating $\mathrm{SrTiO_3}$ is controlled via an electrostatic side gate. Drain-source I/V-curves have been measured at low and elevated temperatures. The transistor shows strong electric-field and temperature-dependent behaviour with a steep sub-threshold slope %of up to as small as $10\:\mathrm{mV/decade}$ and a transconductance as high as $g_m\approx 22 \: \mathrm{μA/V}$. A fully consistent transport model for the drain-source tunneling reproduces the measured steep sub-threshold slope.

cond-mat.mes-hall↗

arXiv2019

Monocrystalline free standing 3D yttrium iron garnet magnon nano resonators

Nano resonators in which mechanical vibrations and spin waves can be coupled are an intriguing concept that can be used in quantum information processing to transfer information between different states of excitation. Until now, the fabrication of free standing magnetic nanostructures which host long lived spin wave excitatons and may be suitable as mechanical resonators seemed elusive. We demonstrate the fabrication of free standing monocrystalline yttrium iron garnet (YIG) 3D nanoresonators with nearly ideal magnetic properties. The freestanding 3D structures are obtained using a complex lithography process including room temperature deposition and lift-off of amorphous YIG and subsequent crystallization by annealing. The crystallization nucleates from the substrate and propagates across the structure even around bends over distances of several micrometers to form e.g. monocrystalline resonators as shown by transmission electron microscopy. Spin wave excitations in individual nanostructures are imaged by time resolved scanning Kerr microscopy. The narrow linewidth of the magnetic excitations indicates a Gilbert damping constant of only $α= 2.6 \times 10^{-4}$ rivalling the best values obtained for epitaxial YIG thin film material. The new fabrication process represents a leap forward in magnonics and magnon mechanics as it provides 3D YIG structures of unprecedented quality. At the same time it demonstrates a completely new route towards the fabrication of free standing crystalline nano structures which may be applicable also to other material systems.

cond-mat.mes-hall↗