Ionic liquid (IL) gating has emerged as a powerful tool to control the structural, electronic, optical, and magnetic properties of materials by driving ion motion at solid interfaces. In magneto-ionic systems, electric fields are used to move ions, typically oxygen, from a donor layer into an underlying magnetic metal. Although oxygen distribution is key to enabling precise and stable control in magneto-ionic systems, the spatial distribution and voltage-dependence of oxygen incorporation in such nanoscale stacks remain unknown. Here, we quantify oxygen depth profiles and oxide formation in Si/SiO2/Ta(15)/HfO2(t) films after IL gating as a function of the gate voltage and HfO2 capping thickness (t = 2 and 3 nm). X-ray reflectivity and X-ray photoelectron spectroscopy measurements revealed a threshold electric field of ≈-2.8 MV/cm to initiate oxygen migration from HfO2 into metallic Ta. The resulting Ta2O5 thickness increases linearly with gate voltage, reaching up to 4 nm at -3 V gating. Notably, the required electric field rises with oxide thickness, indicating a progressively growing barrier for thicker oxide films. The Ta/Ta2O5 interface remains atomically sharp for all gate voltages. This suggests that complete Ta2O5 layers form sequentially before further oxygen penetration, with no sign of deeper diffusion into bulk Ta. Thinner capping layers enhance oxidation, relevant for optimized stack design. Additionally, indium migration from the indium tin oxide electrode to the sample surface was observed, which should be considered for surface-sensitive applications. These insights advance design principles for magneto-ionic and nanoionic devices requiring precise interface engineering.

Forecasting complex, chaotic signals is a central challenge across science and technology, with implications ranging from secure communications to climate modeling. Here we demonstrate that magnons, the collective spin excitations in magnetically ordered materials, can serve as an efficient physical reservoir for predicting such dynamics. Using a magnetic vortex-state microdisk as a magnon-scattering reservoir, we show that intrinsic nonlinear interactions transform a simple microwave input into a high-dimensional spectral output suitable for time-series predictions. Trained on the Mackey-Glass benchmark, which generates a cyclic yet aperiodic time series, the system achieves accurate and reliable predictions that rival other state-of-the-art physical reservoirs. We further identify key design principles: spectral resolution governs the tradeoff between dimensionality and accuracy, while combining multiple device geometries systematically improves performance. These results establish magnonics as a promising platform for unconventional computing, offering a path toward scalable and CMOS-compatible hardware for real-time prediction tasks.

Co₂MnGa is a magnetic Weyl semimetal with strong potential for spintronic and high-frequency device applications. Understanding its magnetization dynamics is essential for reliable device performance. Despite its potential, Co₂MnGa thin films face significant hurdles due to the high energy demands and the difficulty of growing high-quality thin-film heterostructures with clean interfaces. In this study, we performed in-plane ferromagnetic resonance (FMR) measurements on Co₂MnGa films grown on the three different substrates MgO, SiO2 and LiNbO3 (LNBO) to address the effect of substrate choice on its film growth and magnetization dynamics. The frequency dependence of the resonance field and linewidth reveals how substrate selection influences the magnetic damping accordingly.

Topologically nontrivial magnetic textures such as skyrmions offer promising opportunities for spintronic applications. In recent years, it has been shown that the magnetic properties of layered materials can be affected by depositing chiral molecules on the surface, while the influence of chiral overlayers on skyrmion properties such as their stability and interactions remains largely unexplored. To address this challenge, we employ wide-field nitrogen-vacancy (NV) magnetometry to directly image skyrmions in chiral-molecule-functionalized magnetic thin films, enabling quantitative mapping of magnetic stray fields over extended areas under ambient conditions. Using pixel-resolved optically detected magnetic resonance (ODMR) combined with controlled magnetic fields, we reproducibly nucleate and probe skyrmion states in CoFeB ferromagnetic samples, enabling quantitative investigation of their properties. We find evidence for enantioselective and magnetic-field-polarity-dependent modifications of skyrmion diameter, spacing, and shape, pointing to a possibility of molecular control of topological spin textures via magneto-chiral coupling.

We measure picosecond dynamics of labyrinthine stripe domains with chiral Néel-type domain walls using time-resolved x-ray resonant magnetic scattering (XRMS). At the stripe-domain wavevector, the helicity-summed signal shows ultrafast demagnetization, recovery, and a weak oscillatory contribution that we identify as a signature of laser-launched coherent surface phonons. In contrast, the dichroic signal, which is sensitive to the in-plane magnetization inside the Néel walls, shows a strong oscillatory response whose frequency decreases with increasing pump fluence. We attribute this softening to pump-induced changes in the effective anisotropy and saturation magnetization, which modify the restoring field of an internal domain-wall mode. Time-resolved XRMS thus isolates wall-specific dynamics and provides access to internal domain-wall motion in disordered stripe textures on picosecond time scales.

Quantifying particle interactions is central to understanding and controlling collective dynamics in particle-based devices such as those comprising skyrmion ensembles. Here we directly visualize, in real time, the nanosecond current-driven dynamics of an antiferromagnetic skyrmion lattice. By tuning the spin–orbit torque relative to local pinning, we identify two regimes: an incoherent flow, where mobile skyrmions are driven toward pinned neighbours undergoing compression followed by a recoil, and a coherent flow regime, where the lattice translates uniformly. We use an inverse analysis method based on the Thiele equation to extract an exponentially decaying antiferromagnetic skyrmion interaction potential, which is in agreement with simulation results. At higher current densities, the lattice exhibits coherent motion free from detectable Hall and inertial effects or dynamical deformation, and this enables robust ultrafast operation. These findings establish a quantitative framework for antiferromagnetic skyrmion interactions and demonstrate deterministic control of their collective dynamics, even in the incoherent flow regime, thereby providing potential applications for multiskyrmion spintronic devices. Understanding the time-resolved dynamics of antiferromagnetic skyrmion interactions remains a challenge, limiting control over their collective behaviour. Now their ultrafast dynamics is visualized in real time in thin-film multilayers.

We explore the large magnetoresistance (MR) in hBN/few-layer-graphene/CrSBr/few-layer-graphene heterostructures and reveal the mechanism behind its non-monotonic bias dependence. Using bias voltage and temperature as independent tuning knobs, we achieve MR up to 350 at 20K, characterized by symmetric M-shaped maxima around ± 0.5 V. Continuous tuning of the magnetization angle θ via a hard-axis magnetic field shows that the barrier band-edge offset varies linearly with cos(θ/2), a first-order signature of spin-dependent interlayer hybridization. This linear relationship rules out the Jullière model and a spin-filter projection. We conclude that the magnetic-configuration-dependent band edge, rather than electrode spin polarization, dictates the large magnetoresistance in CrSBr junctions.

We demonstrate a grazing-incidence X-ray platform that simultaneously records time-resolved grazing-incidence small-angle X-ray scattering (GISAXS) and grazing-incidence X-ray diffraction (GID) from a femtosecond-laser-irradiated gold film above the melting threshold, with picosecond resolution using an X-ray free-electron laser (XFEL). By tuning the X-ray incidence angle, the probe depth is set to tens of nanometres, enabling depth-selective sensitivity to near-surface dynamics. GISAXS resolves ultrafast changes in surface nanomorphology (correlation length, roughness), while GID quantifies subsurface lattice compression, grain orientation, melting and recrystallization. The approach overcomes photon-flux limitations of synchrotron grazing-incidence geometries and provides stringent, time-resolved benchmarks for complex theoretical models of ultrafast laser-matter interaction and warm dense matter. Looking ahead, the same depth-selective methodology is well suited to inertial confinement fusion (ICF): it can visualize buried-interface perturbations and interfacial thermal resistance on micron to sub-micron scales that affect instability seeding and burn propagation.

Recent predictions of orders of magnitude larger orbital current effects compared to spin currents have attracted significant interest. However, the full potential of giant orbital currents remains to be fully harnessed, since so far, the orbital currents need to be converted into spin currents before they can interact with the static magnetization that is dominated by spin angular momentum in conventional magnets. By using a magnet dominated by orbital angular momentum, we demonstrate a more than fifty-fold enhancement in orbital Hall magnetoresistance in CoO/Cu*, compared to conventional CoO/Pt. This is found to be driven by a unique interaction between dynamic orbital angular momentum from surface oxidized Cu* (i.e., the orbital current) and the static orbital angular momentum which constitutes the magnetic moments in the antiferromagnetic insulator CoO. A distinctive scattering mechanism for orbital currents at the CoO interface leads to a sign reversal in orbital magnetoresistance in CoO/Cu* compared to CoO/Pt. Our results show how by using orbital angular momentum-dominated materials such as CoO, we can harness the benefits of giant orbital currents that have not been possible using conventional spin-dominated magnets, for orbitronics-based devices, offering unprecedented energy efficiency for operations of antiferromagnets that combine ultimate stability with THz dynamics.

Understanding spin dynamics at ever shorter time and smaller length scales is one of the major challenges in fundamental and applied magnetism, leading in particular to the discovery of giant magnetoresistance and All-Optical Switching (AOS) of magnetization and motivating the development of large-scale facilities such as x-ray free-electron lasers. Here, we propose a conceptually distinct approach to explore ultrafast laser-induced spin dynamics at the nanoscale by combining tabletop Magnetic Force Microscopy (MFM) with femtosecond laser excitation. By writing magnetic domains not with a single but with a pair of mutually delayed ultrashort laser pulses, we observe the spin dynamics by analyzing the final static nanotextured domain pattern as a function of pump-to-pump delay. We show that using MFM, we are able to deduce not only the average reversed magnetization but also the switched areas of nanoscale domains with picosecond temporal resolution. The capabilities of the technique are further demonstrated by applying it to study ultrafast helicity-dependent AOS of magnetization in ferromagnetic Pt/Co/Pt, where magnetization can be reversed with a pair of 100-fs and 3-ps laser pulses. Tracking the laser-induced area of the nanotextured domains as a function of the time separation between the pump pulses reveals critical slowing down of the spin dynamics near the Curie temperature of Co, thereby increasing the efficiency of dual-pulse AOS.

Controlling magnetic textures at ever smaller length scales and timescales is of fundamental and technological interest. External stimuli capable of acting at the nanoscale pose a challenge, motivating alternative approaches that exploit the intrinsic inhomogeneity of magnetic textures. Here we use a Pt/Co/Pt ferromagnetic thin film to investigate magnetization reversal with circularly polarized picosecond laser pulses. Magnetic force microscopy reveals stochastic nucleation of complex nanotextured domains from an initial monodomain state. Subsequent illumination of these domains with laser pulses induces deterministic and homogeneous magnetization switching. We find that the domain growth depends on the complexity of the texture, revealing a helicity- and texture-dependent mechanism that contrasts with temperature-gradient-driven domain expansion. We complement our observations with a stochastic model in which domain nucleation is governed by light helicity and the local magnetic environment. These results provide an insight into the mechanism of multipulse helicity-dependent all-optical switching.

Altermagnets have recently attracted considerable interest due to their unique symmetry-governed spintronic properties. Here, we investigate phonon-induced magnon spin currents in a two-dimensional altermagnet. Starting from a microscopic theory of the coupled magnon-phonon system, we derive the nonequilibrium magnon distribution generated by selective phonon excitations. We show that the resulting spin currents exhibit a pronounced d-wave symmetry with respect to the phonon momentum. Moreover, the spin current along the altermagnetic directions can be completely reversed by tuning the phonon frequency. These findings establish altermagnets as promising platforms for realizing highly tunable, phonon-driven coherent terahertz magnon spin currents.

Two-dimensional (2D) particle systems, such as magnetic skyrmions, exhibit topological phase transitions between unique 2D phases. However, a simple and computationally efficient methodology to capture lattice configurational properties and construct an appropriate, easily calculable indicator for phase identification remains elusive. Here, we propose an indicator for topological phase transitions using persistent homology (PH). PH provides a complementary topological description by capturing persistent features derived from the configurational properties of the lattice. The proposed persistent-homology-based indicator, which selectively counts stable features in a persistence diagram, effectively traces the lattice’s ordering changes, as confirmed by comparisons with the conventionally used measure of the ordering (the magnitude of the orientational order parameter ⟨|Ψ6|⟩), typically used to identify lattice phases. We demonstrate the applicability of our indicator to experimental data, showing that it yields results consistent with those of simulations. This experimental validation highlights the robustness of the proposed method for real physical systems beyond idealized simulated systems. While our method is demonstrated in the context of skyrmion lattice systems, the approach is general and can be extended to other two-dimensional systems composed of interacting particles. The proposed topological indicator remains computationally tractable for the system sizes considered here, while preserving the topological invariant-based structural information.

Noncollinear antiferromagnets can generate a transverse electrical response known as the anomalous Hall effect, even though they possess almost no net magnetization. The microscopic origin of this behaviour, however, has remained unclear because conventional measurement geometries mix different contributions to the measured response. Here, we show that applying magnetic fields in selected in-plane directions allows us to disentangle the mechanisms underlying the Hall effect in a representative noncollinear antiferromagnet. By suppressing any dipole-related signal, we isolate a purely octupole-driven Hall response that exhibits a characteristic three-fold angular symmetry. At low magnetic fields, we further observe an additional Hall-like contribution that arises from the scalar spin chirality associated with noncoplanar spin textures. Combining symmetry analysis, first-principles calculations, and transport measurements, we reveal that octupole order, dipole moments, and chirality coexist and contribute in distinct field regimes. These findings establish a framework for identifying and controlling complex magnetic order parameters for spintronic applications.

Spin-orbit torque has emerged as a leading strategy for low-power magnetisation switching in modern spintronics. To date, most efforts have focused on boosting spin currents via the spin Hall effect, exploiting only the electron's spin while largely ignoring its orbital angular momentum. Meanwhile, deterministic switching of perpendicular magnetic anisotropy layers typically requires an external in-plane field to break inversion symmetry, adding power overhead and hindering large-scale deployment. Here, we demonstrate energy-efficient field-free magnetisation switching enabled by spin reorientation in a synthetic antiferromagnetic structure and enhanced by orbital torque. By tuning the exchange coupling field and magnetic anisotropy of the synthetic antiferromagnetic samples, we achieved a magnetisation switching of 96% utilising both spin and orbital torque. Furthermore, increasing the orbital Hall layer thickness by 15 nm leads to an 85% enhancement of damping-like torque efficiency compared to the reference sample with a Pt layer as the spin source. These results demonstrate orbital angular momentum transport as an efficient torque-generation mechanism in synthetic antiferromagnetic heterostructures, offering a scalable route toward low-power spintronic devices.

Ruthenium dioxide (RuO2) has recently emerged as an altermagnetic candidate, but its intrinsic magnetic ground state in thin films remains widely debated. This study aims to clarify the nature and spatial extent of the magnetic order in RuO2 thin films grown under different conditions. Thin films of RuO2 with thicknesses of 30 and 33 nm are deposited by pulsed laser deposition and sputtering onto TiO2(110) and Al2O3(1¯102) substrates, respectively. Low-energy muon spin rotation/relaxation (LE-μSR) with depth-resolved sensitivity measurements is performed in transverse magnetic fields (TF) from 4 K to 290 K. The μSR data collected with a muon implantation energy of 1 keV reveal that magnetic signals originate from the near-surface region of the film (≲10 nm), and the affected volume fraction is approximately 8.5%. The localized magnetic response is consistent across different substrates, growth techniques, and parameter sets, suggesting a common origin related to surface defects and dimensionality effects. The combined use of TF-μSR and the study of depth-dependent implantation with low-energy muons provides direct evidence for surface-confined, inhomogeneous static magnetic order in RuO2 thin films, helping reconcile discrepancies. These findings underscore the importance of considering reduced-dimensional contributions and motivate further investigation into the role of defects, strain, and stoichiometry on the magnetic properties of RuO2, especially at the surface.

Abstract Non-flat energy landscapes leading to localized pinning of skyrmions pose an unavoidable challenge for studies of fundamental 2D spin structure dynamics and applications. Accounting for pinning is a key requirement for predictive modeling of skyrmion systems, impacting the system’s dynamics and introducing randomizing effects. We image skyrmions using magneto-optical Kerr microscopy on a magnetic thin film and analyze their hopping dynamics within the non-flat energy landscape. To achieve a fully quantitative model, we utilize diffusion and dwell times at pinning sites in both experiment and a coarse-grained Thiele model to determine simulation parameters and extrapolate the pinning energy landscape into regions that cannot be sampled within reasonable experimental timespans. We show a direct conversion between simulation and experimental units, the missing key step previously preventing quantitative quasiparticle modeling. We demonstrate our approach’s predictive power and ability for predictive in-silico prototyping of skyrmion devices by measuring the density dependence of skyrmion diffusion, showing excellent agreement with simulation predictions.

Abstract Exciton dissociation in semiconducting nanostructures is crucial for optoelectronic applications, especially when free-carrier generation is required. Despite considerable research, the question of whether and how such generation occurs in strongly excitonic systems remains elusive. Here, we use one-dimensional precision graphene nanoribbons (GNRs) as a model system to investigate exciton dissociation. We systematically explore the interplay between ribbon length (l), excitation energy, and band dispersion in various precision GNRs. Ultrafast Terahertz conductivity measurements reveal that hot exciton dissociation dominates carrier generation, with ribbon length significantly influencing free carrier lifetimes. We identify a critical Bjerrum length (R B) of approximately 20 nm that determines whether photoexcited hot carriers in GNRs can dissociate before forming tightly bound excitons. For shorter ribbons (l < 2R B), rapid ~ps exciton formation prevails. Furthermore, the charge-carrier band dispersion in GNRs plays a critical role in determining dissociation efficiency. Long GNRs with strongly dispersed bands, and consequently low effective carrier masses, exhibit higher mobilities that promote efficient hot-exciton dissociation. These results advance fundamental understanding of dimensionality, energetics, and electronic structure in excitonic materials, providing design principles for optoelectronic devices based on excitonic materials.

Individual, scannable nitrogen vacancy (NV) centers in single crystal diamond nanostructures enable nanoscale, quantitative imaging of magnetic stray fields. Nevertheless, important parameters like distance between the NV center and the sample and the orientation of the NV high symmetry axis are often not known precisely and enter data evaluation as free fitting parameters. We here use scanning NV imaging on micro-patterned, perpendicularly magnetized stripes and discs. From these measurements, we directly infer NV - sample distance d_NV and the NV's azimuthal orientation without the need for an external vector magnet control. We determine d_NV = 31.5 nm, while we infer the azimuthal orientation with a precision of 3°. We additionally employ commercially available silicon needles to image the apex topography of our diamond nanostructures to detect surface contamination. Simultaneously, monitoring NV fluorescence as a function of the needle's position allows us to estimate the lateral placement of the NV inside the diamond nanostructure.

Recent predictions of orders of magnitude larger orbital current effects compared with spin currents have attracted considerable interest. However, orbital currents must first be converted into spin currents to interact with the static magnetization dominated by spin angular momentum in conventional magnets. By using a magnet dominated by orbital angular momentum (OAM), we demonstrate a 70-fold enhancement in orbital Hall magnetoresistance in cobalt II oxide/copper (CoO/Cu*), compared with spin Hall magnetoresistance in cobalt II oxide/platinum (CoO/Pt). This arises from interactions between dynamic OAM from surface-oxidized Cu* and static OAM in the antiferromagnetic insulator CoO. Our results show how by using OAM-dominated materials, we can harness the benefits of giant orbital currents that have not been possible using conventional spin-dominated magnets.