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Altermagnetism represents an emergent collinear magnetic phase with compensated order and an unconventional alternating even-parity wave spin order in the non-relativistic band structure. We investigate directly this unconventional band splitting near the Fermi energy through spin-integrated soft X-ray angular resolved photoemission spectroscopy. The experimentally obtained angle-dependent photoemission intensity, acquired from epitaxial thin films of the predicted altermagnet CrSb, demonstrates robust agreement with the corresponding band structure calculations. In particular, we observe the distinctive splitting of an electronic band on a low-symmetry path in the Brilliouin zone that connects two points featuring symmetry-induced degeneracy. The measured large magnitude of the spin splitting of approximately 0.6 eV and the position of the band just below the Fermi energy underscores the significance of altermagnets for spintronics based on robust broken time reversal symmetry responses arising from exchange energy scales, akin to ferromagnets, while remaining insensitive to external magnetic fields and possessing THz dynamics, akin to antiferromagnets. The fundamental hallmark of altermagnetism lies in the spin splitting of electronic valence bands. Here, the authors observe splitting in metallic CrSb, revealing an exceptionally large value and energetic placement just below the Fermi energy.

Magnetic skyrmions and hopfions are topological solitons 1 —well-localized field configurations that have gained considerable attention over the past decade owing to their unique particle-like properties, which make them promising objects for spintronic applications. Skyrmions 2 , 3 are two-dimensional solitons resembling vortex-like string structures that can penetrate an entire sample. Hopfions 4 – 9 are three-dimensional solitons confined within a magnetic sample volume and can be considered as closed twisted skyrmion strings that take the shape of a ring in the simplest case. Despite extensive research on magnetic skyrmions, the direct observation of magnetic hopfions is challenging 10 and has only been reported in a synthetic material 11 . Here we present direct observations of hopfions in crystals. In our experiment, we use transmission electron microscopy to observe hopfions forming coupled states with skyrmion strings in B20-type FeGe plates. We provide a protocol for nucleating such hopfion rings, which we verify using Lorentz imaging and electron holography. Our results are highly reproducible and in full agreement with micromagnetic simulations. We provide a unified skyrmion–hopfion homotopy classification and offer insight into the diversity of topological solitons in three-dimensional chiral magnets. Transmission electron microscopy is used to observe three-dimensional topological solitons known as hopfions that in a chiral magnet are found to form rings around skyrmion strings, and a nucleation protocol for these rings is provided.

Cubic‐phase GeMnTe2 shows high potential to replace state‐of‐the‐art rhombohedral GeTe for medium temperature thermoelectric application owing to its lower cost. The high structural symmetry can also suppress phase transition during service and provides a superior platform for further band and microstructural engineering. Through Sb2Te3 alloying and Pb substitution, this study realizes a superior peak figure of merit of ≈1.5 at 773 K and a remarkable average figure of merit of ≈0.96 at 323–823 K. Sb2Te3 alloying successfully generates high‐density localized van der Waals (vdW) gaps which are able to scattering low‐frequency phonons effectively for reduced lattice conductivity; meanwhile, it also enlarges the valence band degeneracy for enhanced power factor. Pb substitution further reduces the hole concentration to an optimal level. The achievements in this work well reveal the efficacy of construing localized vdW gaps in improving matrix material's thermoelectric performance, thus might shed light on other cubic or pseudo‐cubic thermoelectric systems. Sb2Te3 alloying generates high‐density localized van der Waals gaps in cubic Ge0.45Mn0.55Te matrix, resulting in electron‐phonon decoupling and improved thermoelectric figure of merit ZT.

Magnetic skyrmions are stable topological solitons with complex non-coplanar spin structures. Their nanoscopic size and the low electric currents required to control their motion has opened a new field of research, skyrmionics, that aims for the usage of skyrmions as information carriers. Further advances in skyrmionics call for a thorough understanding of their three-dimensional (3D) spin texture, skyrmion–skyrmion interactions and the coupling to surfaces and interfaces, which crucially affect skyrmion stability and mobility. Here, we quantitatively reconstruct the 3D magnetic texture of Bloch skyrmions with sub-10-nanometre resolution using holographic vector-field electron tomography. The reconstructed textures reveal local deviations from a homogeneous Bloch character within the skyrmion tubes, details of the collapse of the skyrmion texture at surfaces and a correlated modulation of the skyrmion tubes in FeGe along their tube axes. Additionally, we confirm the fundamental principles of skyrmion formation through an evaluation of the 3D magnetic energy density across these magnetic solitons. Holographic vector-field electron tomography reveals the three-dimensional magnetic texture of Bloch skyrmion tubes in FeGe at nanometre resolution, including complex three-dimensional modulations and fundamental skyrmion formation principles.

Metallic nanoparticles are essential materials in various applications, such as nanomedicine, nanotechnology, and catalysis. While it is known that their catalytic performance is determined by their microstructure and thus by their preparation, the influence of an important but commonly used calcination treatment during nanoparticle preparation on their properties is often overlooked. Herein, structural and morphological changes during the calcination of Pd(NO3)2/ZnO are studied systematically by performing in situ heating experiments mimicking typical preparation conditions, by employing environmental scanning transmission electron microscopy. The effect of different calcination parameters on Pd(NO3)2/ZnO is explored and guidance to enhance control over the preparation of small supported nanoparticles is provided. It is shown that a calcination treatment of Pd(NO3)2/ZnO between 200 and 400 °C for 15–120 min is ideally suited to obtain particles smaller than 4 nm with a narrow size distribution. Based on a systematic investigation of calcination parameters, highly dispersed PdO particles smaller than 4 nm are studied during calcining at 200–400 °C for 2 h. Environmental scanning transmission electron microscopy reveals that temperatures above 400 °C promote particle mobility and agglomeration, leading to an increase in particle size.

The current-driven movement of magnetic skyrmions along a nanostripe is essential for the advancement and functionality of a new category of spintronic devices resembling racetracks. Despite extensive research into skyrmion dynamics, experimental verification of current-induced motion of ultra-small skyrmions within an ultrathin nanostripe is still pending. Here, we unveil the motion of individual 80 nm-size skyrmions in an FeGe track with an ultrathin width of 100 nm. The skyrmions can move steadily along the track over a broad range of current densities by using controlled pulse durations of as low as 2 ns. The potential landscape, arising from the magnetic edge twists in such a geometrically confined system, introduces skyrmion inertia and ensures efficient motion with a vanishing skyrmion Hall angle. Our results showcase the steady motion of skyrmions in an ultrathin track, offering a practical pathway for implementing skyrmion-based spintronic devices. The authors study the dynamics of 80 nm-size skyrmions in a 100 nm-wide track by electrical Lorentz transmission electron microscopy. They show that the skyrmions can be moved by nanosecond current pulse without experiencing the skyrmion Hall effect.

A fundamental property of particles and antiparticles (such as electrons and positrons, respectively) is their ability to annihilate one another. A similar behaviour is predicted for magnetic solitons 1 —localized spin textures that can be distinguished by their topological index Q . Theoretically, magnetic topological solitons with opposite values of Q , such as skyrmions 2 and their antiparticles (namely, antiskyrmions), are expected to be able to continuously merge and annihilate 3 . However, experimental verification of such particle–antiparticle pair production and annihilation processes has been lacking. Here we report the creation and annihilation of skyrmion–antiskyrmion pairs in an exceptionally thin film of the cubic chiral magnet of B20-type FeGe observed using transmission electron microscopy. Our observations are highly reproducible and are fully consistent with micromagnetic simulations. Our findings provide a new platform for the fundamental studies of particles and antiparticles based on magnetic solids and open new perspectives for practical applications of thin films of isotropic chiral magnets. Magnetic skyrmions—a type of localized spin texture—have been theoretically predicted to annihilate with counterparts known as antiskyrmions. By means of electron microscopy, such annihilation has now been observed in a cubic chiral magnet.

Skyrmions are vortex-like spin textures that form strings in magnetic crystals. Due to the analogy to elastic strings, skyrmion strings are naturally expected to braid and form complex three-dimensional patterns, but this phenomenon has not been explored yet. We found that skyrmion strings can form braids in cubic crystals of chiral magnets. This finding is confirmed by direct observations of skyrmion braids in B20-type FeGe using transmission electron microscopy. The theoretical analysis predicts that the discovered phenomenon is general for a wide family of chiral magnets. These findings have important implications for skyrmionics and propose a solid-state framework for applications of the mathematical theory of braids. Skyrmions are topological two-dimensional spin textures that in three-dimensional systems resemble strings or tubes. Here, using transmission electron microscopy Zheng et al observe the braiding of skyrmion strings in FeGe and predict this phenomenon for a large family of magnets.

Chiral magnetic skyrmions1,2 are nanoscale vortex-like spin textures that form in the presence of an applied magnetic field in ferromagnets that support the Dzyaloshinskii–Moriya interaction (DMI) because of strong spin–orbit coupling and broken inversion symmetry of the crystal3,4. In sharp contrast to other systems5,6 that allow for the formation of a variety of two-dimensional (2D) skyrmions, in chiral magnets the presence of the DMI commonly prevents the stability and coexistence of topological excitations of different types7. Recently, a new type of localized particle-like object—the chiral bobber (ChB)—was predicted theoretically in such materials8. However, its existence has not yet been verified experimentally. Here, we report the direct observation of ChBs in thin films of B20-type FeGe by means of quantitative off-axis electron holography (EH). We identify the part of the temperature–magnetic field phase diagram in which ChBs exist and distinguish two mechanisms for their nucleation. Furthermore, we show that ChBs are able to coexist with skyrmions over a wide range of parameters, which suggests their possible practical applications in novel magnetic solid-state memory devices, in which a stream of binary data bits can be encoded by a sequence of skyrmions and bobbers.

The rapid development of electron tomography, in particular the introduction of novel tomographic imaging modes, has led to the visualization and analysis of three-dimensional structural and chemical information from materials at the nanometre level. In addition, the phase information revealed in electron holograms allows electrostatic and magnetic potentials to be mapped quantitatively with high spatial resolution and, when combined with tomography, in three dimensions. Here we present an overview of the techniques of electron tomography and electron holography and demonstrate their capabilities with the aid of case studies that span materials science and the interface between the physical sciences and the life sciences.