Engineering the dispersion relation is one of the key ingredients enabling the application of spin waves in computational elements. One way to engineer the spin-wave band structure is to create an artificial magnonic crystal, which can be used to design specific band gaps or dispersion branches. However, creating a two-dimensional magnonic crystal usually requires removing material, which dramatically decreases the decay lengths of spin waves. Here, we present a method to manipulate the demagnetizing field landscape by utilizing large-area curvilinear nanotemplates consisting of three-dimensional nanopyramids arranged in a square lattice with a period of 400 nm. In a 50-nm-thick Permalloy film grown on these curvilinear templates, we experimentally observe a complete in-plane band gap together with flat-band modes that exhibit strong real-space localization of the spin waves in the pyramid valleys. Micro-focused Brillouin light scattering measurements corroborate the numerically predicted dispersion and reveal the possibility of opening and closing this gap by varying the external magnetic field. Our results establish three-dimensional-templated continuous films as a versatile platform for two-dimensional signal processing and magnonic computing elements.

Magnetostrictive materials are of interest not only from a fundamental perspective but also for their potential applications, spanning spintronics to energy harvesting. A new magnetostrictive material-SmFe5As3-reveals a complex interplay between magnetostriction, magnetic properties, and the crystal structure behavior. The ground state of SmFe5As3 is ferrimagnetic, as evidenced by magnetic susceptibility data, band-structure calculations, and XANES measurements. At T m 1 = 28 ± 4 $T_{m1} = 28 \pm 4$ K, part of the Fe sublattice reorients, transitioning into a ferromagnetic state. This is followed by an entrance into the paramagnetic state at T m 2 = 76 ± 4 $T_{m2} = 76 \pm 4$ K. The effects observed in the magnetic measurements are accompanied by structural phase transitions. All three phases-below T m 1 $T_{m1}$ , between T m 1 $T_{m1}$ and T m 2 $T_{m2}$ , and above T m 2 $T_{m2}$ -are described by the same structural motif of the UCr5P3 type (monoclinic space group P 2 1 / m $P2_1/m$ ), differing only in the degree of deformation of the Fe-As framework. The new material exhibits giant magnetostriction of 2500 × 10 - 6 $2500 \times 10^{-6}$ . Dilatometry measurements on a SmFe5As3 single crystal indicate strongly diverse behavior, exhibiting not only negative, but also zero, as well as positive thermo-elastic effects.

Magnetic hysteresis curves, measured by MOKE magnetometry, should be interpreted with caution, as their recorded local characteristics can vary significantly depending on the sample location. Therefore, conclusions about sample parameters (such as coercive field strength) do not necessarily reflect the characteristics of the entire sample. This is especially true if MOKE magnetometry is performed with probing spot sizes very much smaller than some characteristic domain size or sample area covered by domain nuclei. In this article this is demonstrated for magnetic films with perpendicular anisotropy by measuring polar MOKE loops in a wide-field Kerr microscope. On the examples of Co/Pt films with different domain nucleation behaviour we show that the locally measured coercive field may vary up to several ten percent and that the spot size, from which the Kerr signal is recorded, needs to comprise a critical number of at least domain nuclei to obtain coercivities that are relevant for the whole specimen. We furthermore demonstrate that the speed of loop recording strongly matters in perpendicular media due to domain wall creeping effects.

Tailoring ferroic textures and stray field landscapes is central to many magnetic functionalities. However, creating complex textures by design remains very challenging. Here, we present a simple and versatile strategy to create a wide range of periodic magnetic textures by application of a homogeneous magnetic field and a geometrical transformation of a 2D film into a rolled-up 3D architecture and back. The magnetization configuration imprinted in the 3D state is determined by the magnetic anisotropy of the material and its local orientation with respect to the field axis. Upon transforming the film back to the 2D state, the angular magnetization configuration encoded in the 3D state is converted into a spatially periodic magnetic pattern. Using this technique, we have realized distinct periodic magnetization patterns in 2D, such as up-down magnetization patterns in an out-of-plane exchange-bias material, head-to-head/tail-to-tail configurations in in-plane exchange-bias materials, and spin-spiral-like magnetization patterns in an isotropic exchange-bias material. To create the spin-spiral pattern, we have developed an isotropic exchange-biased material system, in which magnetization can be stabilized with remanence to saturation ratio (m r/m s) approximate to 0.9 along any chosen axis by magnetic annealing. The spin-spiral-like magnetization pattern created through this technique is inaccessible through alternative domain patterning techniques.

ZUSAMMENFASSUNG Magnetostriktive Materialien sind nicht nur aus rein wissenschaftlicher Sicht von Interesse, sondern auch im Hinblick auf mögliche Anwendungen, die von Spintronik bis zur Energiegewinnung reichen. Ein neues magnetostriktives Material – SmFe 5 As 3 – zeigt ein komplexes Zusammenspiel zwischen Magnetostriktion, magnetischen Eigenschaften und der Kristallstruktur. Der Grundzustand von SmFe 5 As 3 ist ferrimagnetisch, was durch magnetische Suszeptibilitätsdaten, Bandstrukturrechnungen und XANES‐Messungen belegt wird. Bei = 28 4 K ordnet sich ein Teil des magnetischen Fe‐Untergitters neu an und geht in einen ferromagnetischen Zustand über. Darauf folgt bei = 76 4 K der Übergang in den paramagnetischen Zustand. Die in den magnetischen Messungen beobachteten Effekte werden von strukturellen Phasenübergängen begleitet. Alle drei Phasen – unterhalb von , zwischen und sowie oberhalb von – werden durch denselben strukturellen Motif vom UCr 5 P 3 ‐Typ (monokline Raumgruppe ) beschrieben und unterscheiden sich lediglich im Grad der Verformung der Fe–As Teilstruktur. Das neue Material zeigt eine riesige Magnetostriktion von . Dilatometrische Messungen an einem SmFe 5 As 3 ‐Einkristall weisen auf ein stark anisotropes Verhalten hin, das sowohl negatives, konstantes sowie positives thermoelastisches Verhalten zeigt.

This paper reports Bitter method observations of pentagon-shaped magnetic domains on the surface of an FeGa single crystal. These domains intersect parallel Landau-Lifshitz-type domains, termed herein banded domains. The pentagon domains are shown to exhibit peculiar segmented zigzag boundaries distinct from the well known 180° V-lines of the banded domains. To analyze the micromagnetic structure of pentagon domains, domain responses to a perpendicular magnetic field are examined. In particular, the magnetization directions of the pentagon domains and adjacent banded domains are determined via the perpendicular magnetic field-induced spike domain configurations. The subsurface structure of the pentagon domains is then inferred, revealing that the segmented zigzag boundaries actually consist of four types of 90° V-lines. These findings based on the Bitter observations are subsequently verified using the Kerr microscopy technique. The coexistence of 90° V-lines and 180° V-lines as two types of zigzag boundaries in FeGa further clarifies the origin of zigzag boundaries, which lies at the heart of a significant scientific controversy regarding the magnetic domain phenomena in Fe-based magnetostrictive materials.

ABSTRACT Magnetostrictive materials are of interest not only from a fundamental perspective but also for their potential applications, spanning spintronics to energy harvesting. A new magnetostrictive material—SmFe 5 As 3 —reveals a complex interplay between magnetostriction, magnetic properties, and the crystal structure behavior. The ground state of SmFe 5 As 3 is ferrimagnetic, as evidenced by magnetic susceptibility data, band‐structure calculations, and XANES measurements. At K, part of the Fe sublattice reorients, transitioning into a ferromagnetic state. This is followed by an entrance into the paramagnetic state at K. The effects observed in the magnetic measurements are accompanied by structural phase transitions. All three phases—below , between and , and above —are described by the same structural motif of the UCr 5 P 3 type (monoclinic space group ), differing only in the degree of deformation of the Fe–As framework. The new material exhibits giant magnetostriction of . Dilatometry measurements on a SmFe 5 As 3 single crystal indicate strongly diverse behavior, exhibiting not only negative, but also zero, as well as positive thermo‐elastic effects.

Materials with a first-order magnetic phase transition demonstrate colossal changes in physical properties near the phase transition temperature. However, the mechanisms of phase transition occurrence are not fully understood. In this work, using the Fe48Rh52 alloy as an example, we study the near-surface magnetic and structural properties of the alloy near the phase transition temperature. Analysis of images obtained using the magnetooptic Kerr effect at different temperatures allowed us to separate the contributions from nucleation and growth of the ferromagnetic phase during the phase transition. Approximation of experimental data by the proposed model allowed us to estimate the surface energy of ferromagnetic clusters with different micromagnetic structures. The work also shows the influence of microscopic features on the formation of macroscopic properties of the alloy.

Cylindrical ferromagnetic tubes are notable for their geometry-driven physical phenomena, making them promising for future technological applications. Self-assembly rolling technology is used to create tubes with high surface quality and side edges, which are crucial for customizing magnetic anisotropy through magnetostatic interactions at the edges. This study investigates the anisotropy induced by these interactions in magnetostriction-free permalloy membranes. Thin planar membranes of varying dimensions were transformed into tubular structures with curvature radii in the tens of microns and winding numbers from 0.6 to 1.5. Experimental results reveal that magnetostatic energy is minimized when the winding number exceeds 0.8–0.9 by adopting an azimuthal domain pattern, or flux-closure configuration, from previously axial domains. These results are supported by analytical calculations of the equilibrium magnetic state of both planar and curved membranes, considering shape anisotropy constants. These constants were derived from magnetostatic energy calculations assuming a single domain configuration and applied to various geometries and curvatures. This research advances the understanding of anisotropy tuning in curved thin-film architectures, focusing on achieving azimuthal magnetic anisotropy in soft ferromagnetic tubular structures without additional induced anisotropy, a key step for applications in data storage, field sensors, and biomedicine relying on 3D magnetic structures.

Modification of the magnetic properties under the induced strain and curvature is a promising avenue to build three-dimensional magnetic devices, based on the domain wall motion. So far, most of the studies with 3D magnetic structures were performed in the helixes and nanowires, mainly with stationary domain walls. In this study, we demonstrate the impact of 3D geometry, strain and curvature on the current-induced domain wall motion and spin-orbital torque efficiency in the heterostructure, realized via a self-assembly rolling technique on a polymeric platform. We introduce a complete 3D memory unit with write, read and store functionality, all based on the field-free domain wall motion. Additionally, we conducted a comparative analysis between 2D and 3D structures, particularly addressing the influence of heat during the electric current pulse sequences. Finally, we demonstrated a remarkable increase of 30% in spin-torque efficiency in 3D configuration.

Curvilinear magnetism emerged as a new route to tailor properties of magnetic solitons by the choice of geometry and topology of a magnetic architecture. Here, we develop an anodized aluminum oxide template-based approach to realize hierarchical 3D magnetic nanoarchitectures of nanoflower shape. The technique provides defect-free regular arrays of magnetic nanoflowers of tunable shape with a period of 400 nm over cm2 areas. We combined advanced magnetic imaging methods with micromagnetic simulations to study complex magnetic states in nanoflowers originating due to magnetostatics-driven symmetry break in curvilinear nanomembranes. An interaction between surface and volume magnetostatic charges in 3D curved nanoflowers leads to the stabilization of asymmetric and shifted vortices as well as states with two Bloch lines. Ordered large area arrays of complex-shaped magnetic nanoarchitectures developed in this work are relevant for prospective research on 3D magnonics and spintronics.

The potential of wide-field magneto-optical Kerr microscopy for the characterisation of low-dimensional van-der-Waals crystals is explored using the example of Cr2Ge2Te6 flakes in the ten nanometers thickness range. Although the magnetic domains with an expected width in the hundred-nanometer range cannot be seen on this material due to the limited lateral resolution, we show that Kerr microscopy is nevertheless a very valuable method for measuring the magnetization loops on selectable thickness regions on the flake. From the loop character one can indirectly infer on the existence or suppression of band domains, which are the equilibrium patterns above a film thickness of about 7nm. We derived this characteristic thickness from the initial susceptibility of the hysteresis loops and used it to estimate the specific domain wall energy to be $2.7\cdot 10^{-\mathrm {4}}$ J/m2. We further demonstrate a thickness- and light colour dependent sign inversion of the Kerr signal that is explained by a Fresnel-type depth sensitivity concept. Accordingly, the Kerr contrast is governed by the relative phase of the Kerr amplitude that can be freely adjusted by a rotatable compensator. The compensator is thus the decisive optical element in magneto-optical Kerr magnetometry and microscopy on low-dimensional materials. It needs to be appropriately aligned to avoid a cancelation of the Kerr contrast and to maximise the Kerr signal.

Combining wide-field magneto-optical Kerr microscopy with a time-lapse analysis scheme allows investigating magnetization fluctuations with high spatial as well as temporal resolution. We here use this technique to study magnetization fluctuations in a thin ferromagnetic film prepared into a quasi-equilibrium magnetic state via a dedicated field sweep protocol. Our experiments reveal spatially localized noise hotspots distributed across the sample surface within the magnetic domains in the quasi-equilibrium state. The spatial density of the noise hot spots is very similar at different low magnetic field strengths, as expected from the fluctuation-dissipation theorem. The measurement scheme thus opens the way for the spatially resolved investigation of quasi-equilibrium noise processes in magnetic materials.

The structural and magnetic properties of sputter-deposited Fe100-xRux films were studied for x <= 50. The crystal structure of Fe100-x Ru-x is shown to be predominantly body-centered cubic for x<13 and to undergo a gradual transition to hexagonal close-packed in the Ru concentration range 13<x <20. Magnetic measurements indicate that the addition of Ru to Fe gives rise to a noncollinear magnetic alignment between Fe atoms in the body-centered cubic FeRu alloys, while the hexagonal close-packed FeRu alloys exhibit paramagnetic behavior. A simple atomistic model was used to show that the competition between ferromagnetic coupling of neighboring Fe atoms and antiferromagnetic coupling of Fe atoms across Ru atoms in cubic FeRu structures can induce noncollinear magnetic order. Magnetic multilayer structures used in thin-film magnetic devices make extensive use of both Fe and Ru layers. Our results reveal that the presence of even a small amount of Ru in Fe influences the magnetic order of Fe, which could impact the performance of these devices.

The potential of wide-field magneto-optical Kerr microscopy for the characterisation of low-dimensional van-der-Waals crystals is explored using the example of Cr2Ge2Te6 flakes in the ten nanometers thickness range. Although the magnetic domains with an expected width in the hundred-nanometer range cannot be seen on this material due to the limited lateral resolution, we show that Kerr microscopy is nevertheless a very valuable method for measuring the magnetization loops on selectable thickness regions on the flake. From the loop character one can indirectly infer on the existence or suppression of band domains, which are the equilibrium patterns above a film thickness of about 7nm. We derived this characteristic thickness from the initial susceptibility of the hysteresis loops and used it to estimate the specific domain wall energy to be 2.7 & sdot;10(-4 )J/m(2). We further demonstrate a thickness- and light colour dependent sign inversion of the Kerr signal that is explained by a Fresnel-type depth sensitivity concept. Accordingly, the Kerr contrast is governed by the relative phase of the Kerr amplitude that can be freely adjusted by a rotatable compensator. The compensator is thus the decisive optical element in magneto-optical Kerr magnetometry and microscopy on low-dimensional materials. It needs to be appropriately aligned to avoid a cancelation of the Kerr contrast and to maximise the Kerr signal.

Fast growth of sustainable energy production requires massive electrification of transport, industry and households, with electrical motors as key components. These need soft magnets with high saturation magnetization, mechanical strength, and thermal stability to operate efficiently and safely. Reconciling these properties in one material is challenging because thermally-stable microstructures for strength increase conflict with magnetic performance. Here, we present a material concept that combines thermal stability, soft magnetic response, and high mechanical strength. The strong and ductile soft ferromagnet is realized as a multicomponent alloy in which precipitates with a large aspect ratio form a Widmanstätten pattern. The material shows excellent magnetic and mechanical properties at high temperatures while the reference alloy with identical composition devoid of precipitates significantly loses its magnetization and strength at identical temperatures. The work provides a new avenue to develop soft magnets for high-temperature applications, enabling efficient use of sustainable electrical energy under harsh operating conditions.