Soft magnetic actuators capable of fast, remote, and untethered motion are increasingly sought for microscale robotic systems. Here, we introduce compact ceramic-based, magnetically responsive microscroll actuators inspired by the coiled geometry of the butterfly proboscis. The actuators are fabricated from hybrid films composed of aligned vanadium pentoxide (V2O5) nanofibers and Fe3O4 nanoparticles distributed within the nanofiber matrix, forming a flexible, laminated architecture with enhanced mechanical robustness. Using a razor blade-assisted scrolling method, the planar films are transformed into tightly wound microscrolls with tunable geometry and micrometer scale diameters. Under near-field magnetic stimulation (∼60 mT), the scrolls exhibit rapid, reversible, and multidirectional actuation with angular displacements of up to 180°. The actuation relies on a dual magneto-mechanical mechanism: distributed magnetic stresses generated by the embedded Fe3O4 phase initiate unrolling, while residual elastic strain stored during scrolling drives the re-rolling motion. This geometry-programmed actuation enables a lifting ratio of 32.5× relative to actuator mass, a work density of ∼8.1 kJm- 3, and a footprint reduction of up to 96%. Notably, the ceramic-based microscrolls retain structural and functional integrity over 5000 magnetic actuation cycles, demonstrating a durable architecture-driven route toward untethered soft robotic microsystems.

Curvature reshapes magnetization when a structure's dimensions approach intrinsic magnetic length scales, but functional magnetic colloids and microrobots are often micrometers in size, where the radius of curvature exceeds these scales by several orders of magnitude. Whether particle diameter remains an effective parameter for tuning magnetic response in this regime is therefore unclear. We synthesized partially ordered FePt Janus caps on spherical SiO_2 particles with diameters of 3–10 μm, characterized their structure and magnetic response, and extended the investigated range to 1–20 μm using micromagnetic simulations. Across this range, coercivity, remanence, and hysteresis-loop shape showed no systematic dependence on particle diameter in either experiment or simulation. The ratio between exchange length and radius of curvature (ℓ_ex/R ∼ 10^-3–10^-4) places these particles in a locally planar regime where diameter-dependent curvature effects are weak. Size and magnetic response are therefore effectively decoupled within the investigated regime: particle diameter can be selected according to transport, payload, and biocompatibility requirements without introducing a measurable magnetic penalty, but it does not provide an effective route for tuning magnetization reversal. Instead, the magnetic response is governed primarily by material state, including the balance between magnetically hard L1_0 and soft A1 FePt, with additional modulation by processing-induced morphology. The resulting length-scale map identifies the regime in which this decoupling is expected to hold and where diameter-dependent curvature effects may become significant.

Epitaxial thin-film heterostructures of the strongly spin-orbit coupled Mott-insulator Sr2IrO4 (SIO) and the cuprate high temperature superconductor YBa2Cu3O7 - delta (YBCO) are grown with pulsed laser deposition (PLD). A high crystalline quality is confirmed with X ray diffraction. The magnetic order of single SIO layers is studied with dc magnetization and low-energy muon spin rotation measurements and resembles that of the bulk material with a canted antiferromagnetic order. The electronic normal state and superconducting properties of YBCO (10, 12, or 14 nm)-SIO (20 nm) and inversely stacked SIO (20nm)-YBCO (10, 12, or 14 nm) bilayers are studied with dc resistivity measurements and found to be strongly dependent on the sequence of the layer stacking. The YBCO-SIO bilayers with d(YBCO) = 14nm, 12 nm, and 10 nm are all metallic and superconducting with an onset temperature around 85K and zero resistivity below 65K. To the contrary, for the inversely stacked SIO-YBCO bilayers a metallic and superconducting response occurs only at d(YBCO) = 14 nm, whereas and 10 nm are electronic insulators. This highlights that a long-ranged localization and/or depletion of the YBCO charge carriers occurs at the SIO-YBCO interface that is very anomalous and remains to be understood.

Many electronic and electrochemical devices rely on the exchange of light elements such as hydrogen and oxygen with the environment. Understanding and tailoring the device functionality requires accurate information about the concentration and chemical bonding of such species inside a solid, which is particularly difficult if several species are exchanged. In LaNiO3 thin films in situ transport experiments reveal a re-entrant metal-insulator transition upon hydrogen exposure. The origin of this unusual behavior can be understood by combining information about the stoichiometry and chemical bonding of hydrogen and oxygen as determined by neutron reflectometry and x-ray absorption spectroscopy, respectively. In addition to the metallic parent phase, an insulating phase with composition LaNiO2.65 and a re-entrant metallic phase with composition LaNiO2.15(OH)0.5 are identified. They can be inter-converted by redox reactions in different external environments. The methodology employed offers new insights into the mechanisms underlying the influence of hydrogen in functional devices.

Fluoride-Ion-Batteries are a promising battery technology to achieve high energy densities exceeding those of traditional lithium-ion batteries. Reports on intercalation-based electrode materials for Fluoride-Ion-Batteries have mostly focused on cathode materials, while only a few intercalation-based anode materials have been reported. Their performance was heavily affected by carbon-based reductive side reactions, limiting reversibility and introducing high overpotentials. In this study, we present the successful substitution of carbon by metallic copper in solid-state FIBs, enabling the use of La2NiO3F2, Pr2NiO3F2, Sr2TiO3F2 and Sr3Ti2O5F4 as intercalation-based anode materials by avoiding parasitic side reactions associated with the conductive carbon additive.

Nanodiamond In article number 2310109, Metin Sitti and co-workers demonstrate paramagnetic centers in nanodiamond to provide strong signal enhancement in magnetic resonance images (MRI). The use of nanodiamond addresses the need for alternative non-metal based T1-contrast agents and challenges associated with the use of gadolinium based contrast agents for cell labeling and tracking.

Thin buried magnetic layers ranging from thicknesses of a few atomic monolayers to several nanometers are omnipresent in the fields of magnetism and spintronics. For the functionality and fine tuning of devices build with such layers, exact knowledge of the depth dependent magnetic properties is essential. Especially the interfacial magnetic properties are important. Hence, understanding how magnetism is affected by structural variations, such as thickness or interface roughness, is mandatory. In this study, we use x-ray resonant magnetic reflectometry and magnetometry to study the high-resolution depth dependent magnetization profiles of thin magnetic transition metal layers sandwiched between an oxide and chromium layer. Compared to bulk materials, the room temperature saturation magnetization of these layers is reduced by up to 67%. These reductions are extremely sensitive to small structural variations. From the magnetic depth profiles, we disentangle different effects contributing to the magnetization reduction and the exact magnetic properties of the interface.

Interlayer exchange coupling has been intensively studied for over 30 years and has been successfully incorporated into almost all magnetic thin-film devices. In this study we find that antiferromagnetic interlayer exchange coupling can be achieved across, and improved by, spacer layers containing over 60 at.% of magnetic material. Measurements of sputtered Fe-doped spacer layers with x-ray magnetic circular dichroism reveal that the magnetic atoms in such spacer layers retain a large magnetic moment. The addition of magnetic atoms to the spacer layer is shown to double the coupling strength, leading to the largest-ever-observed antiferromagnetic bilinear coupling strength in magnetic multilayers deposited by magnetron sputtering, which is the industrial technique of choice. Electronic structure calculations in this work predict an experimentally obtained dependence of interlayer exchange coupling on both the magnetic material concentration and the spacer-layer thickness, in contrast with the prevailing understanding of interlayer exchange coupling.

Interface engineering in complex oxide superlattices is a growing field, enabling manipulation of the exceptional properties of these materials, and also providing access to new phases and emergent physical phenomena. Here we demonstrate how interfacial interactions can induce a complex charge and spin structure in a bulk paramagnetic material. We investigate a superlattice (SLs) consisting of paramagnetic LaNiO3 (LNO) and highly spin-polarized ferromagnetic La2/3Ca1/3MnO3 (LCMO), grown on SrTiO3 (001) substrate. We observed emerging magnetism in LNO through an exchange bias mechanism at the interfaces in X-ray resonant magnetic reflectivity. We find non-symmetric interface induced magnetization profiles in LNO and LCMO which we relate to a periodic complex charge and spin superstructure. High resolution scanning transmission electron microscopy images reveal that the upper and lower interfaces exhibit no significant structural variations. The different long range magnetic order emerging in LNO layers demonstrates the enormous potential of interfacial reconstruction as a tool for tailored electronic properties.

Magnetic multilayers with a separating insulating layer are used in a multitude of functional devices. Controlling the magnetic properties of such devices with an electric field has the potential to vastly enhance their performance. Nevertheless, experimental methods to study the origin of electric-field-induced effects on buried interfaces remain elusive. By using element selective x-ray resonant magnetic reflectometry we are able to gain access to changes in the electronic structure of interfacial atoms caused by an electric field. With this method it is possible to probe interfacial states at the Fermi energy. In a multilayer stack with a Ni/SiO_{2} interface, we find that the electric field slightly shifts the Ni L_{3}-edge in energy, which indicates a change of the oxidation state of interfacial Ni atoms. Further analysis of the strength of the effect reveals that only about 30% of the electrons moved by the electric field end up in interfacial Ni states.

Quantitative approaches in clinical Magnetic Resonance Imaging (MRI) benefit from the availability of adequate phantoms. Ideally, the phantom material should reflect the complexity of signals encountered in vivo . In the present study we validate and characterize clusters consisting of sodium-polyacrylate embedded in an alginate matrix that are unloaded or loaded with iron for Quantitative Susceptibility Mapping (QSM), yielding a non-uniform iron distribution and tissue-mimicking MRI properties. Vibrating sample magnetometry (VSM) was used to characterize the phantom material and verify the accuracy of previous MRI-based observations of the QSM-based molar susceptibility ( χM ). MRI at 14.1 T with high resolution acquisitions was used to determine the size of hydrogel clusters and to further investigate the suitability of the phantom material as a model system for QSM at high field. VSM demonstrated that the iron-solution used for manufacturing the phantoms consisted of ferric iron. The χM of clusters with a constant iron-to-polyacrylate-ratio (8.3 μg/mg) observed with VSM was 50.7 ± 8.0 ppb mM −1 but showed a tendency towards saturation at total iron concentrations >1 mM. On unwrapped and background corrected phase-images obtained with gradient-echo MRI and an isotropic voxel size of 37 μm at 14.1T, the iron-free clusters had a roundish shape and blurry border with an equivalent sphere diameter of 276 ± 230 µm and a QSM of 7 ± 7 ppb. Iron-loading led to strong phase wrapping, necessitating the use of short echo times, or short inter-echo delays below 10 ms at 14.1 T. The equivalent sphere diameter of the iron-loaded clusters was estimated to 400–500 µm as verified using different MRI modalities (spin-echo, inversion recovery, and gradient echo MRI). With a constant iron-to-polyacrylate ratio, the cluster density was 10 mm −3 mM −1 iron. In agreement with previous observations, χM of samples with a constant amount of polyacrylate was 50.6 ± 11.4 ppb mM −1 at 3 T while samples containing clusters with a constant iron-to-polyacrylate-ratio yielded χM = 56.1 ± 6.3 ppb mM −1 at 3T and 55.6 ± 0.7 ppb mM −1 at 14.1 T. In conclusion we found that the molar susceptibility of the proposed model system corresponds to that predicted for ferritin in vivo loaded with 3000 iron atoms. The reproducibility was within 12% across MR scanners, batches, and phantom types and compared well with results obtained with vibrating sample magnetometry.

The recently discovered 2D magnets represent versatile building blocks for spintronic devices. In particular, the out-of-plane 2D ferromagnets Fe3GeTe2 and Cr2Ge2Te6 (CGT) are attracting strong attention, owing to their ability to host topological spin textures. Among these, CGT is particularly interesting, as its semiconducting property could facilitate electric field control over the spin textures. Here, we systematically explore the magnetic phases of an exfoliated CGT flake with a thickness on the order of 50 nm by scanning transmission x-ray microscopy using three different measurement protocols. The domain periodicity was found to decrease with increasing temperature and decreasing flake thickness, the latter of which can be attributed to the relatively small magnetic anisotropy of CGT. Moreover, the magnetic phase diagram of CGT features a high-temperature skyrmion phase pocket, and skyrmionium formation occurs upon zero-field cooling. The sensitivity of the skyrmions to magnetic field changes indicates that dipolar interactions play a major role in stabilizing these magnetic spin textures.

Being able to accurately control the interaction of spin waves is a crucial challenge for magnonics in order to offer an alternative wave-based computing scheme for certain technological applications. Especially in neural networks and neuromorphic computing, wave-based approaches can offer significant advantages over traditional CMOS-based binary computing schemes with regard to performance and power consumption. In this work, we demonstrate precise modulation of phase- and amplitude-sensitive interference of coherent spin waves in a yttrium–iron–garnet based magnonic analog adder device, while also showing the feasibility of frequency-division multiplexing. Using time-resolved scanning transmission x-ray microscopy, the interference was directly observed, giving an important proof of concept for this kind of analog computing device and its underlying working principle. This constitutes a step toward wave-based analog computing using magnons as an information carrier.

The recent claim of superconductivity above room temperature in Pb10−xCux(PO4)6O with 0.9 < x < 1 (referred to as LK-99) has sparked considerable interest. To minimize the influence of structural defects and impurity phases on the physical properties, we have synthesized phase-pure single crystals with a copper doping level of x ∼ 1. We find that the crystals are highly insulating and optically transparent. X-ray analysis reveals an uneven distribution of the substituted Cu throughout the sample. Temperature (T) dependent magnetic susceptibility measurements for 2 ≤ T ≤ 800 K reveal the diamagnetic response characteristic of a non-magnetic insulator, as well as a small ferromagnetic component, possibly originating from frustrated exchange interactions in Cu-rich clusters in the Pb10−xCux(PO4)6O structure. No anomalies indicative of phase transitions are observed. We, therefore, rule out the presence of superconductivity in Pb9Cu(PO4)6O crystals and provide some considerations on the origin of anomalies previously reported in experiments on polycrystalline specimens.

Here, we report a novel and conceptually straightforward technique to detect the spin-polarization directly, with laser spot spatial resolution, at buried ferromagnet/insulator interfaces in ambient settings. This has been accomplished by monitoring the voltage-induced change of the longitudinal MOKE signal as a function of the applied magnetic field and applying an AC voltage across the interface. For the case where the spin polarization enters the VMOKE signal, a simple quantitative model is proposed. A distinct positive majority spin polarization has been found for Fe and Co, whereas Ni exhibits a negative minority spin polarization.

Nanodiamonds (ND) hold great potential for diverse applications due to their biocompatibility, non-toxicity, and versatile functionalization. Direct visualization of ND by means of non-invasive imaging techniques will open new venues for labeling and tracking, offering unprecedented and unambiguous detection of labeled cells or nanodiamond-based drug carrier systems. The structural defects in diamonds, such as vacancies, can have paramagnetic properties and potentially act as contrast agents in magnetic resonance imaging (MRI). The smallest nanoscale diamond particles, detonation ND, are reported to effectively reduce longitudinal relaxation time T1 and provide signal enhancement in MRI. Using in vivo, chicken embryos, direct visualization of ND is demonstrated as a bright signal with high contrast to noise ratio. At 24 h following intravascular application marked signal enhancement is noticed in the liver and the kidneys, suggesting uptake by the phagocytic cells of the reticuloendothelial system (RES), and in vivo labeling of these cells. This is confirmed by visualization of nanodiamond-labeled macrophages as positive (bright) signal, in vitro. Macrophage cell labeling is not associated with significant increase in pro-inflammatory cytokines or marked cytotoxicity. These results indicate nanodiamond as a novel gadolinium-free contrast-enhancing agent with potential for cell labeling and tracking and over periods of time.

Frequency multiplication is an essential part of electronics and optics which led to numerous indispensable ap-plications. In this paper, we utilize a combination of scanning transmission x-ray microscopy and micromagnetic simulations to directly image magnonic frequency multiplication by means of dynamic real-space magnetization measurements. We experimentally demonstrate frequency multiplication up to the seventh order, which enables the generation of nanoscale spin waves at 6 GHz with excitation frequencies of less than 1 GHz. Good agreement between the experiment and micromagnetic simulations allows us to build a micromagnetic model capable of predicting conversion efficiencies and multiplexing capabilities of the system. Furthermore, simulations reveal that more than two rows of antidots do not increase the conversion efficiency substantially. By enabling magnonic multiplexing with low input frequencies while not exceeding the size of a few microns, the device will lead to numerous applications, further advancing the capabilities of magnonic data transmission.

Magnetic droplets are non-topological magnetodynamical solitons displaying a wide range of complex dynamic phenomena with potential for microwave signal generation. Bubbles, on the other hand, are internally static cylindrical magnetic domains, stabilized by external fields and magnetostatic interactions. In its original theory, the droplet was described as an imminently collapsing bubble stabilized by spin transfer torque and, in its zero-frequency limit, as equivalent to a bubble. Without nanoscale lateral confinement, pinning, or an external applied field, such a nanobubble is unstable, and should collapse. Here, we show that we can freeze dynamic droplets into static nanobubbles by decreasing the magnetic field. While the bubble has virtually the same resistance as the droplet, all signs of low-frequency microwave noise disappear. The transition is fully reversible and the bubble can be thawed back into a droplet if the magnetic field is increased under current. Whereas the droplet collapses without a sustaining current, the bubble is highly stable and remains intact for days without external drive. Electrical measurements are complemented by direct observation using scanning transmission x-ray microscopy, which corroborates the analysis and confirms that the bubble is stabilized by pinning.

The discovery of two-dimensional magnets has initiated a new field of research, exploring both fundamental low-dimensional magnetism, and prospective spintronic applications. Recently, observations of magnetic skyrmions in the 2D ferromagnet Fe3GeTe2 (FGT) have been reported, introducing further application possibilities. However, controlling the exhibited magnetic state requires systematic knowledge of the history-dependence of the spin textures, which remains largely unexplored in 2D magnets. In this work, we utilise real-space imaging, and complementary simulations, to determine and explain the thickness-dependent magnetic phase diagrams of an exfoliated FGT flake, revealing a complex, history-dependent emergence of the uniformly magnetised, stripe domain and skyrmion states. The results show that the interplay of the dominant dipolar interaction and strongly temperature dependent out-of-plane anisotropy energy terms enables the selective stabilisation of all three states at zero field, and at a single temperature, while the Dzyaloshinksii-Moriya interaction must be present to realise the observed Néel-type domain walls. The findings open perspectives for 2D devices incorporating topological spin textures.

A key element to tailor the properties of magnetic multilayers is the coupling between the individual magnetic layers. In case of skyrmion hosting multilayers, coupling of skyrmions across the magnetic layers is highly desirable. Here the magnetic interlayer coupling was studied in epitaxial all-oxide heterostructures of ferromagnetic perovskite SrRuO_3 layers separated by spacers of the strong spin-orbit coupling oxide SrIrO_3. This combination of oxide layers is being discussed as a potential candidate system to host Néel skyrmions. First order reversal curve (FORC) measurements were performed in order to distinguish between magnetic switching processes of the individual layers and to disentangle the signal of soft magnetic impurities from the samples' signal. Additionally, FORC investigations enabled to determine whether the coupling between the magnetic layers is ferromagnetic or antiferromagnetic. The observed interlayer coupling strength was weak for all the heterostructures, with SrIrO_3 spacers between 2 monolayers and 12 monolayers thick.