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Funding Information: This work was supported by the Academy of Finland (Grant Nos. 317918, 325480, and 338748). Lithography and FIB milling were performed at the OtaNano-Micronova Nanofabrication Center and the OtaNano-NanoMicroscopy Center, respectively, supported by Aalto University. Computational resources were provided by the Aalto Science-IT project. We thank Helmholtz-Zentrum Berlin for the allocation of synchrotron radiation beamtime. We report the imaging of short-wavelength spin waves in a continuous nanometer-thick YIG film with a Co stripe patterned on top. Dynamic dipolar coupling between the YIG film and the Co stripe lowers the spin-wave wavelength when spin waves enter the YIG/Co bilayer region from the bare YIG film, causing partial reflection at the YIG/Co edge. We use time-resolved scanning transmission x-ray microscopy to image the mode conversion process down to a wavelength of 280 nm and extract the spin-wave dispersion, decay length, and magnetic damping in the YIG/Co bilayer. We also analyze spin-wave reflection from the YIG/Co edge and its dependence on the wavelength of incoming and transmitted spin waves.

Funding Information: Maxime Vergès was supported by a CIFRE Ph.D. grant from Vinci Technologies. This work was supported by the ANR‐20‐CE09‐0013 UFO, by the Institute Carnot ICEEL for the project “CAPMAT” and FASTNESS, by the Région Grand Est, by the Metropole Grand Nancy, for the Chaire PLUS by the impact project LUE‐N4S, part of the French PIA project “Lorraine Université d'Excellence” reference ANR‐15‐IDEX‐04‐LUE, by the “FEDERFSE Lorraine et Massif Vosges 2014–2020”, a European Union Program, and by the Academy of Finland (grant no. 316857). The devices in the present study were patterned at MiNaLor platform that is partially funded by Grand Est Region and Feder through RaNGE project. Publisher Copyright: © 2022 The Authors. Advanced Science published by Wiley-VCH GmbH. The impact of plasmonic surface lattice resonances on the magneto-optical properties and energy absorption efficiency has been studied in arrays of [Co/Gd/Pt]N multilayer nanodisks. Varying the light wavelength, the disk diameter, and the period of the array, it is demonstrated that surface lattice resonances allow all-optical single pulse switching of [Co/Gd/Pt]N nanodisk arrays with an energy 400% smaller than the energy needed to switch a continuous [Co/Gd/Pt]N film. Moreover, the magneto-optical Faraday effect is enhanced at the resonance condition by up to 5,000%. The influence of the disk diameter and array period on the amplitude, width and position of the surface lattice resonances is in qualitative agreement with theoretical calculations and opens the way to designing magnetic metasurfaces for all-optical magnetization switching applications.

The impact of plasmonic surface lattice resonances on the magneto-optical properties and energy absorption efficiency has been studied in arrays of [Co/Gd/Pt]

Unlike classic synthetic stimulus-responsive and shape-memory materials, which remain limited to fixed responses, the responses of living systems dynamically adapt based on the repetition, intensity, and history of stimuli. Such plasticity is ubiquitous in biology, which is profoundly linked to memory and learning. Concepts thereof are searched for rudimentary forms of "intelligent materials." Here, we show plasticity of electroconductivity in soft ferromagnetic nickel colloidal supraparticles with spiny surfaces, assembling/disassembling to granular conducting micropillars between two electrodes driven by magnetic field

Funding Information: This work was supported by the Academy of Finland (Grants No. 295269, No. 306978, and No. 327804). K.R.E. acknowledges funding from the NSF (Grant No. NSF-MPS-2006456). E.G. was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo -FAPESP (Grant No. 18/19586-9). T.A.-N. has been supported in part by the Academy of Finland QTF CoE Grant No. 312298. Publisher Copyright: © 2022 American Physical Society. Magnetic skyrmions are topologically distinct particles whose thermally activated motion could be used to implement probabilistic computing paradigms. While solid-liquid phase transitions in skyrmion lattices have been demonstrated, the behavior of a skyrmion liquid and the effects of pinning are largely unknown. Here we demonstrate the formation of a weakly pinned skyrmion liquid in a magnetic heterostructure. By inserting a Ru wedge layer at the ferromagnet/heavy metal interface we evaluate the dependence of skyrmion dynamics on the skyrmion size and density. Our experiments demonstrate that the diffusion of skyrmions is largest in dense liquids with small skyrmions. The thermal motion of skyrmions at room temperature easily overcomes the narrow distribution of pinning site energies in the granular film structure, satisfying a key requirement of probabilistic device architectures. Micromagnetic simulations support the findings and also reveal the existence of a thermally activated high-frequency collective oscillation.

openaire: EC/H2020/861145/EU//BeMAGIC Funding Information: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 861145. The work was supported by the Academy of Finland (Grant Nos. 317918 and 325480), JST CREST under Grant No. JPMJCR18J1, and JSPS KAKENHI under Grant No. 21H04614. Lithography was performed at the OtaNano—Micronova Nanofabrication Centre of Aalto University. Computational resources were provided by the Aalto Science-IT project. Publisher Copyright: © 2022 Author(s). We report zero-field routing of spin waves in a multiferroic heterostructure comprising a ferromagnetic Fe film and a ferroelectric BaTiO3 substrate with fully correlated strain-coupled domains. In the Fe film, a regular alternation of magnetic anisotropy produces a back-and-forth rotation of uniform magnetization in zero magnetic field. Spin waves propagating across this domain structure are refracted at the magnetic domain walls because of abrupt changes in the dispersion relation and phase velocity. Using super-Nyquist sampling magneto-optical Kerr effect microscopy, we image the routing of spin waves and analyze the dependence of the effect on frequency and the propagation direction. We find that spin waves are routed efficiently by angles up to 60° without measurable loss in amplitude. The experimental results are reproduced by micromagnetic simulations and calculations based on the modified Snell's law for magnonics.

Funding Information: This work was supported by the Academy of Finland (Grant Nos. 295269, 306978, 321983, 325480, and 327804). We acknowledge the provision of computational resources provided by the Aalto Science-IT project. Publisher Copyright: © 2022 Author(s). Active control of propagating short-wavelength spin waves in perpendicularly magnetized materials is promising for designing nanoscale magnonic devices. One method of manipulating spin waves on the nanoscale is through their interaction with magnetic textures, an example of which is the magnetic skyrmion - a particle-like topological object stabilized in thin film heterostructures by the Dzyaloshinskii-Moriya interaction (DMI) and perpendicular magnetic anisotropy. In this paper, the interaction between spin waves and skyrmions is studied using micromagnetic simulations. The magnetic parameters chosen are similar to those found experimentally, leading to a skyrmion with an extended core of reversed magnetization. The effect of a propagating spin wave on the skyrmion is to cause the emission of a secondary spin wave by the skyrmion. At low frequencies, where the incoming spin wave wavelength is much larger than the skyrmion, this leads to a nearly circular re-emitted spin wave. The pattern of emission becomes increasingly complex at higher frequencies as the wavelength becomes similar to the skyrmion size due to the complex excitation of the extended core. The emitted spin wave profile can be controlled by altering the size of the skyrmion through the magnitude of the DMI, providing a method of tuning the system.

Spin waves are studied intensively for their intriguing properties and potential use in future technology platforms for the transfer and processing of information and microwave signals. The development of devices and materials for spin-wave systems requires a lot of measurement time and effort, and thus increasing the measurement throughput by extending the instrumentation capabilities is of the essence. In this letter, we report on a new and straightforward approach to increase the measurement throughput by fully exploiting the wideband detection nature of the Brillouin light scattering technique in single-shot experiments using a white-noise RF generator., Comment: 5 pages + 3 supplementary pages, 4 figures, 3 supplementary figures

We report experimental results on spin-wave propagation, transmission gap tuning, and mode conversion in straight, curved, and Y-shaped yttrium iron garnet waveguides with magnonic crystals made of submicrometer-wide airgrooves. We observe forbidden frequency gaps with sizes up to 200 MHz in straight waveguides and narrowing of the gaps in curved and Y-shaped waveguides. The spin-wave transmission signal is strongly suppressed inside the gaps and remains high at allowed frequencies for all waveguide types. Using super-Nyquist sampling magneto-optical Kerr effect microscopy, we image symmetric and asymmetric spin-wave interference patterns, the self-focusing of propagating spin waves, and interconversions between width modes with different quantization numbers.

Magnetic skyrmions are topologically-distinct swirls of magnetic moments which display particle-like behaviour, including the ability to undergo thermally-driven diffusion. In this paper we study the thermally activated motion of arrays of skyrmions using temperature dependent micromagnetic simulations where the skyrmions form spontaneously. In particular, we study the interaction of skyrmions with grain boundaries, which are a typical feature of sputtered ultrathin films used in experimental devices. We find the interactions lead to two distinct regimes. For longer lag times the grains lead to a reduction in the diffusion coefficient, which is strongest for grain sizes similar to the skyrmion diameter. At shorter lag times the presence of grains enhances the effective diffusion coefficient due to the gyrotropic motion of the skyrmions induced by their interactions with grain boundaries. For grain sizes significantly larger than the skyrmion diameter clustering of the skyrmions occurs in grains with lower magnetic anisotropy., 7 pages, 5 figures

Funding Information: This work was supported by the Academy of Finland (Grant Nos. 316857 and 295269). The authors wish to acknowledge CSC – IT Center for Science, Finland, and the Aalto Science‐IT project for computational resources. Publisher Copyright: © 2022 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH. The voltage control of magnetism is a promising path to the development of low-power spintronic devices. Magneto-ionics—exploiting voltage-driven ion migration to control magnetism—has attracted interest because it can generate large magnetoelectric effects at low voltage. Here, the use of the solid-state lithium-ion battery technology for reversible voltage-controlled switching between perpendicular and in-plane magnetization states in a Co–Pt bilayer is demonstrated. Due to the small size and high mobility of lithium ions, small voltages produce an exceptionally high magnetoelectric coupling efficiency of at least 7700 fJ V–1 m–1 at room temperature. The magnetic switching effect is attributed to the modulation of spin-orbit coupling at the Co–Pt interface when lithium ions migrate between a lithium storage layer (LiCoO2) and the magnetic interface across a lithium phosphorous oxynitride (LiPON) solid-state electrolyte, which is corroborated by density functional theory calculations. Voltage control of magnetism in the battery structure does not show degradation over more than 500 voltage cycles, demonstrating promise for solid-state lithium-based magneto-ionic devices.