Superconducting nickelate thin films with the layered square-planar structure are synthesized via the topotactic reduction of a more oxygen rich perovskite or Ruddlesden-Popper (RP) phase due to the instability of the target ${\mathrm{Ni}}^{1+\delta }$ valence. The topotactic reduction induces a dramatic structural transformation, which yields high defect densities in the resulting film and has introduced uncertainty regarding film uniformity, particularly as it relates to the calculation of physical parameters based on estimates of superconducting volume fraction. Here we use neutron reflectometry (NR) and secondary ion mass spectrometry (SIMS) to obtain a sub-nm resolved understanding of the structural depth profile across a wide range of layered square-planar nickelates. While the as-grown parent compounds are bulklike and of very high quality, the depth profiles of reduced films are generally nonuniform and indicative of partial amorphization. We identify careful selection of substrate and reduction conditions as promising directions toward mitigating amorphization and improving uniformity.

The large van der Waals gap in transition metal dichalcogenides (TMDs) offers an avenue to tune the ground state of 2D materials through the intercalation of magnetic atoms. Here, we investigate the charge correlations in ${\mathrm{Fe}}_{1/3}{\mathrm{TaS}}_2, {\mathrm{Co}}_{1/3}{\mathrm{TaS}}_2$, and ${\mathrm{Fe}}_{0.35}{\mathrm{NbS}}_2$ by combining angle-resolved photoemission spectroscopy (ARPES), x-ray scattering, magnetometry, and density functional theory (DFT). We find that, while short-range charge fluctuations develop in Ta-based compounds, ${\mathrm{Fe}}_{0.35}{\mathrm{NbS}}_2$ exhibits long-range charge order which is strongly coupled with magnetic order and tunable by external magnetic field. Our electronic structure analysis reveals that intercalation reconstructs the Fermi surface via charge transfer and band renormalization, yet does not generate the nesting conditions compatible with the observed ordering vectors. Complementary phonon calculations further exclude a conventional electron-phonon origin of charge order. Together, these results establish magnetoelastic coupling as the dominant mechanism behind charge ordering in ${\mathrm{Fe}}_{0.35}{\mathrm{NbS}}_2$ and highlight the contrasting role of Nb and Ta hosts in stabilizing correlated ground states in intercalated TMDs.

Directional memory in amorphous solids is commonly quantified through the Bauschinger effect, yet the observation of the inverse Bauschinger effect suggests that the sign of memory can invert, pointing to distinct underlying plastic organization. Here, we connect directional memory to the nature of yielding in steadily sheared amorphous solids. Using simulations of two-dimensional polydisperse glasses, we show that the type of directional memory (Bauschinger versus inverse Bauschinger) is jointly controlled by deformation history, strain rate, and parent temperature. We identify a critical history amplitude ${\gamma }_{N,\mathrm{crit}}(T_p,\dot{\gamma })$ and construct a phase diagram that delineates regimes with memory inversion from those showing only conventional Bauschinger response. Microscopically, memory inversion correlates with networklike shear-band morphology and plastic healing, whereas conventional memory is associated with persistent localization and cumulative damage. These results establish directional memory as an order parameter for a shear-rate and annealing-controlled brittle-ductile crossover and suggest that plastic healing provides a generic route to memory inversion in disordered solids.

The realization of air-stable two-dimensional (2D) metals confined at the interface between graphene and SiC has attracted significant attention owing to their distinct properties compared to their bulk counterparts. In this work, we identify two distinct structural phases in a monolayer silver intercalated between graphene and SiC: (i) a moiré pattern arising from the lattice mismatch between graphene and monolayer silver and (ii) a striped reconstruction formed through the interaction with the underlying SiC. Using cryogenic scanning tunneling microscopy combined with density functional theory, we elucidate the origin of the silver striped reconstruction. Driven by the competition between the silver-SiC and the silver-silver interactions within a monolayer, the silver atoms form a one-dimensional Frenkel-Kontorova domain, in which an $(n+1)\times \surd 3$ silver supercell accommodates an $n\times \surd 3$ supercell $(n=20)$ of the underlying SiC, which partially relieves tensile strain, otherwise imposed by ideal epitaxy. The strain-induced reconstruction creates a long-range modulation of 2D silver electronic density, giving rise to an electronic state at $\sim 0.75\mathrm{eV}$ above the Fermi level in the transition regions between different silver-SiC registries. These findings uncover the important interplay between the structural and electronic properties of intercalated 2D metals and the underlying SiC substrate, providing new insights into substrate-mediated reconstruction and electronic modulation at confined interfaces.

Using first-principles calculations and companion experimental validations, we demonstrate that the valence electron concentration (VEC) can be used to self-consistently parameterize the bonding characteristics of high-entropy diborides (HEBs) and in turn predict their mechanical properties. When VEC is 10.0 per formula unit (f.u.), HEBs enter the superhard category where ${\mathrm{H}}_{\mathrm{v}}>40\mathrm{GPa}$ because bonding states are optimally filled to resist shear deformation. Conversely, above or below a VEC of 10.0, the hardness decreases due to the filling of antibonding or the emptying of bonding states of the HEBs, respectively. This result is supported by analyses of the electronic structure, bonding, antibonding, and electronic orbitals’ (metal $d$ and B $2p$) occupation as a function of VEC. To complement the first-principles calculations, four HEBs were synthesized using high power impulse magnetron sputtering to interrogate their crystalline structure and mechanical properties. All HEBs retain a single-phase $\mathrm{Al}{\mathrm{B}}_2$-type hexagonal structure with highly dense nodular grain morphology. Hardness measurements reveal general agreement between theory and experiment. An HEB with VEC of 10.0/f.u. shows superhard characteristics, with micro- and nanoindentation hardness greater than 40 GPa. This combined entropy and VEC-based materials design formulation establishes a foundation for the discovery of high-entropy ceramics with enhanced thermomechanical properties, making them suitable for extreme engineering applications.

In his groundbreaking work on the theory of ferri- and antiferromagnetism, Néel proposed the existence of ferrimagnets with zero net magnetization. These $L$-type ferrimagnets were later termed fully compensated. This study focuses on $L$-type ferrimagnets, particularly Heusler alloys based on vanadium (V), manganese (Mn), iron (Fe), and cobalt (Co). First-principles calculations reveal that these ferrimagnets exhibit anomalous temperature dependence, differing from antiferromagnets. Spin dynamics calculations, based on the calculated exchange coupling coefficients, show that this behavior stems from the ferrimagnets' inequivalent magnetic sublattices, which have distinct exchange interactions. The temperature dependence of the magnetic properties is analyzed through a comparison of the first-principles calculations and Néel's molecular field theory, extended to include Heusler compounds. In addition to exhibiting compensated ferrimagnetic behavior, examining the electronic structure using the Bloch spectral function shows that the investigated Heusler alloys are half-metals which have a full spin polarization at the Fermi energy. The combination of complete magnetic compensation and half-metallicity makes these alloys interesting for fundamental research and spintronics applications because their zero net magnetization minimizes stray fields while retaining half-metallicity.

We introduce and systematically investigate a new class of topological magnetic textures—skyrmionium metamatter—composed of skyrmioniums ($Q=0$) and skyrmions ($Q=-1$) arranged in periodic compound lattices that emulate the structural diversity of atomic materials. We show that pure skyrmionium lattices are intrinsically unstable against elongation distortions and relax into spiral states, whereas the inclusion of even a small fraction of skyrmions suppresses this instability and stabilizes a broad family of mixed skyrmion–skyrmionium crystals. These states are classified by their topological stoichiometry and exhibit multiple metastable polymorphs with distinct plane-group symmetries. Smooth transformations between different polymorphs can be achieved by tuning the lattice periodicity, highlighting the reconfigurability of the metamatter. We further analyze the collective spin dynamics of these composite lattices and uncover a rich hierarchy of excitation modes that extends far beyond those of conventional skyrmion lattices. The coexistence of skyrmions and skyrmioniums gives rise to hybrid collective modes with nontrivial phase relations and deformation-assisted dynamics. Our results establish skyrmionium-based metamatter as a versatile platform for designing tunable, topologically heterogeneous magnetic lattices with emergent structural and dynamical properties, opening new opportunities for reconfigurable magnonic and spintronic functionalities.

${\mathrm{Co}}_2\mathrm{MnGa}$ (CMG), a magnetic Weyl semimetal, exhibits high Curie temperature, ultralow damping, and strong spin-dependent transport properties, favorable for spintronics applications. While its room-temperature magnetization dynamics have been explored, the temperature ($T$) dependence of key dynamic parameters such as damping and exchange stiffness remains underexplored. In this work, we investigate the temperature-dependent magnetization dynamics of sputtered CMG thin films (20, 60, and 80 nm) on MgO substrates. We use broadband ferromagnetic resonance spectroscopy with a magnetic field applied perpendicular to the sample plane to characterize these properties. X-ray diffraction reveals a strain-induced tetragonal distortion originating from the substrate-film lattice mismatch, most pronounced in the 20 nm film. As temperature decreases, the saturation magnetization ($M_s$) deviates from Bloch's law below 170 K, due to a temperature-dependent tetragonal distortion. Furthermore, the effective magnetization $M_{\mathrm{eff}}>M_s$ indicates a net in-plane anisotropy that strengthens with decreasing temperature, while the perpendicular uniaxial anisotropy ($K_{u_{\left[001\right]}}$) also increases, with the 20 nm film exhibiting the highest values across all temperatures. Perpendicular standing spin waves observed in the 60 and 80 nm films enable extraction of the exchange stiffness ($A_{ex}$) and exchange length ($l_{ex}$), both of which increase with decreasing temperature. Furthermore, $A_{ex}$ follows a $T^2$ dependence indicative of a dominant contribution from electron-magnon interactions. Compared to the 80 nm film, the 60 nm film has a larger magnetic domain size as revealed by magnetic force microscopy. All films exhibit ultralow damping at room temperature, with the 80 nm film showing a temperature-independent behavior.

Physical properties intermediate between constituents of alloys can be achieved as downward convex positive bowing, upward concave negative bowing, or zero bowing. Such bowing effects are essential for band gap engineering in semiconductor alloys. Upward band gap bowing effects are rather rare, hindering the exploration on half of the available physical property space of alloys. Part of this being a rare event is related to the need to stabilize an alloy with low mixing enthalpy, so it does not phase separate. In this paper we find via density functional theory that one can satisfy the simultaneous conditions of negative mixing enthalpy and upward band gap bowing in four-component $\mathrm{AB}{\mathrm{X}}_3$ halide perovskite alloys in the cubic perovskite structure. Such perovskite alloys have the B-site occupied by a mixture of group IVB and IIB elements that have the IVB-$s$ and IIB-s states in the valence bands and conduction bands, respectively, leaving the delocalized $s$ states to strongly repel each other. This $s-s$ repulsion leads to the upward band gap bowing and negative mixing enthalpies simultaneously. Remarkably, we identify a perovskite alloy that has a band gap much larger than all its components. Analogous trends of upward band gap bowing and negative mixing enthalpy also appear in the corresponding three-component and two-component $\mathrm{AB}{\mathrm{X}}_3$ halide perovskite alloys. These observations of upward band gap bowing and negative mixing enthalpy will significantly accelerate the design of stable upward band gap bowing alloys in a broad range of material families.

The VCoNi alloy is a face-centered cubic medium-entropy alloy with exceptionally high yield strength, serving as a prototypical system for investigating short-range order and phase stability in compositionally complex alloys. However, density functional theory calculations underestimate the stability of the random solid solution by several hundred Kelvin. To resolve this discrepancy, we present accurate Gibbs energy calculations for both the random solid solution and a prototypical $\mathrm{L}{1}_2$ ordered phase. Our findings reveal that vibrational and electronic excitations account for nearly half of the entropy difference between the ordered phase and disordered solid solution. These factors reduce the energy difference between the two phases by about one-third and help stabilize the solid solution. Our thermodynamic analysis is validated through direct comparison with experimental thermodynamic data.

We demonstrate a thermally activated epitaxy window for the growth of NbO at temperatures exceeding 1000 ${}^{\circ }\mathrm{C}$. NbO films grown in this mode display superior structural and transport properties, which are reproducible across a window of oxygen partial pressure. Through comprehensive analysis, we propose the prototypical electrical properties of NbO. This study unequivocally demonstrates the utility of high temperatures in the thin film synthesis of refractory metal compounds.

Discovery of two-dimensional ferromagnetic van der Waals chromium triiodide (${\mathrm{CrI}}_3$) opens new avenues toward tunable terahertz topological magnon via stacking order control in a multilayer system. We theoretically simulated magnetism and topological magnon modulation in multiple ${\mathrm{CrI}}_3/\mathrm{As}$ stacking orders by means of first-principles and linear spin-wave theory calculations. The first-nearest-neighbor spin-exchange interactions are enhanced up to 100% from those in monolayer ${\mathrm{CrI}}_3$ due to degeneracy lifting in $\mathrm{Cr} d$ orbitals induced by broken symmetry from the addition of $\mathrm{As}$ monolayer. Furthermore, interfacial charge transfer from the $\mathrm{As}$ monolayer to $\mathrm{I}$ atom in the bottom sublayer induces finite Dzyaloshinskii-Moriya interactions of first-nearest-neighboring $\mathrm{Cr}$ atoms and enhances those of second-nearest-neighboring $\mathrm{Cr}$ atoms. Magnon Dirac gaps in bilayer ${\mathrm{CrI}}_3/\mathrm{As}$ are open wider than those in monolayer ${\mathrm{CrI}}_3$ at the edge of the Brillouin zone, attributed to the enhanced second-nearest-neighbor Dzyaloshinskii-Moriya interactions. The magnon dispersion in a nanoribbon geometry exhibits localized magnon edge states, and the existence of localized edge states is unique to a certain periodicity direction relative to the crystallographic direction in the stacking order with broken rotational symmetry.

Predicting the failure and plasticity of solids remains a longstanding challenge, with broad implications for materials design and functional reliability. Disordered solids like metallic glasses can fail either abruptly or gradually without clear precursors, and the mechanical response depends strongly on composition, thermal history, and deformation protocol—impeding generalizable modeling. While deep learning methods offer predictive power, they often rely on numerous input parameters, hindering interpretability, methodology advancement, and practical deployment. We address this longstanding challenge with a macroscopic, physically grounded approach that uses plastic strain accumulation in the elastic regime to robustly predict deformation and yield. This method reduces complexity and improves interpretability, offering a practical alternative for disordered materials. For the Cu-Zr-(Al) metallic glasses prepared with varied annealing, we identify two limiting regimes of plastic strain growth: power law in poorly annealed and exponential in well-annealed samples. A physics-informed framework with Bayesian inference extracts growth parameters from stress-strain data within $\sim 5\%$ strain, enabling early prediction of bulk response and yield point, well before the failure. The predictive performance improves with annealing and bulk plasticity correlates with the microscopic plastic activity from scattered to growth near yielding. This work presents a physically interpretable and experimentally relevant framework for predicting plasticity, stress-strain curve, and failure in metallic glasses from early mechanical response, offering both theoretical insights and practical tools for material characterization and design.

Nitrogen vacancy (NV) centers in proximity of diamond surfaces are promising nanoscale quantum sensors. However, their coherence properties are negatively affected by magnetic and electric surface noise, whose origin and detailed impact have remained elusive. Using atomistic models of diamond surfaces derived with density functional theory, together with decoherence time calculations with cluster correlation expansion methods, we quantify the effects of surface crystallographic orientation and functionalization, and of the density of unpaired electrons on the NV Hahn-echo time ($T_2$). We determine a crossover depth at which $T_2$ ceases to be limited by surface-nuclear spins and recovers the bulk-limited value. We find that for static surface-electron baths, the ratio between the NV depth and the separation between surface electron spins determines a transition from fast-fluctuating to quasi-static noise, leading to a dependence of $T_2$ on orientation for specific surfaces. We also find that the modulation of $T_2$ by spin-phonon relaxations lead to motional‐narrowing at sub-microseconds relaxation times. Importantly, our calculations show that it is only when accounting for the surface spin in-sequence hopping that measured $T_2$ values as a function of depth can be reproduced, thus highlighting the importance of hopping-mediated models to describe the surface spin noise affecting NV sensors. Overall, our work provides clear guidelines for engineering diamond surfaces to achieve enhanced NV coherence for quantum sensing and information processing applications.

Spontaneous formation of a topological spin texture at room temperature under zero magnetic field is vital for advanced spintronics applications. One of the commonly used techniques for probing the formation of such a topological spin texture is the topological Hall effect (THE), which is usually induced by the fictitious field generated by a topological spin texture under a finite magnetic field. Here we report observation of THE under zero magnetic field in a van der Waals magnetic semimetal, $\mathrm{C}{\mathrm{r}}_3\mathrm{T}{\mathrm{e}}_4$. Owing to its high Curie temperature, spontaneous THE survives up to room temperature. Given the easy-plane anisotropy and centrosymmetric nature of $\mathrm{C}{\mathrm{r}}_3\mathrm{T}{\mathrm{e}}_4$, the observed THE signals should be induced by the formation of a magnetic bimeron stabilized by spin frustration. Our findings provide profound insights into the emergence of a topological spin texture in a centrosymmetric van der Waals magnet, taking a big step toward future ultracompact spintronics applications.

The room-temperature optical properties and the influence of light on the magnetic spin dynamics of ${\mathrm{EuZn}}_2{\mathrm{P}}_2$ are studied. Temperature-dependent electron spin resonance (ESR) measurements reveal that spin-spin interactions predominantly govern the spin relaxation mechanisms, as evidenced by the linewidth behavior ($\mathrm{\Delta }H$), whereas positive $g$ shifts ($\mathrm{\Delta }g)$ for $H\parallel ab$ indicate the presence of local electron polarization. The ESR data support the formation of anisotropic magnetic polarons, which trap spin carriers and contribute to increased electrical resistance. Angular-dependent ESR spectra at room temperature display anisotropic behavior in both $\mathrm{\Delta }g\left(\varphi \right)$ and $\mathrm{\Delta }H\left(\varphi \right)$, with a dominant three-dimensional component $C_{3\mathrm{D}}$, indicative of robust interlayer coupling and antiferromagnetic fluctuations. Under the influence of visible light, subtle linewidth broadening and enhanced ESR intensity indicate that photoexcited carriers influence the magnetic relaxation, suggesting a light-induced magnetic response possibly associated with a photomagnetic effect. Electrical transport measurements demonstrate a reproducible photovoltaic effect with a responsivity of $3.78\times {10}^{-3}$ A/W and detectivity of ${10}^{11}$ Jones, comparable to several known intermetallic and semiconductor photodetectors. These findings establish ${\mathrm{EuZn}}_2{\mathrm{P}}_2$ as an excellent platform among Zintl-type antiferromagnets to study the coupling between light matter and suggesting the presence of a possible photomagnetic effect.

Understanding the behavior and evolution of a dynamical many-body system by analyzing patterns in their experimentally captured images is a promising method relevant for a variety of living and nonliving self-assembled systems. The arrays of moving liquid crystal skyrmions studied here are a representative example of hierarchically organized materials that exhibit complex spatiotemporal dynamics driven by multiscale processes. Joint geometric and topological data analysis (TDA) offers a powerful framework for investigating such systems by capturing the underlying structure of the data at multiple scales. In the TDA approach, we introduce the $\mathrm{\Psi }$ function, a robust numerical topological descriptor related to both the spatiotemporal changes in the size and shape of individual topological solitons and the emergence of regions with their different spatial organization. The geometric method based on the analysis of vector fields generated from images of skyrmion ensembles offers insights into the nonlinear physical mechanisms of the system's response to external stimuli and provides a basis for comparison with theoretical predictions. The methodology presented here is very general and can provide a characterization of system behavior both at the level of individual pattern-forming agents and as a whole, allowing one to relate the results of image data analysis to processes occurring in a physical, chemical, or biological system in the real world.

Orbital currents induced by electric fields in transition metals have been experimentally reported in various material systems to date, in the form of orbital torques and orbital accumulation. However, most of these studies have been conducted on polycrystalline systems, and there has been virtually no discussion on their relation to first-principles electronic band structure calculations. In this study, we investigated the orbital Hall effect using epitaxial thin films of Ti, a 3d transition metal in which the spin Hall effect is negligibly small and the orbital Hall effect is dominant. Our first-principles calculations revealed that, within the $\mathrm{Ti}\left(1\overline{1}00\right)$ plane, the magnitude of the orbital Hall conductivity differs depending on whether the electric field is applied along the $\left[0001\right]$ or $\left[11\overline{2}0\right]$ direction. Based on this, we fabricated epitaxial $\mathrm{Ti}\left(1\overline{1}00\right)$ films and detected orbital torque using Ni, which has negligible magnetocrystalline anisotropy. As a result, we observed a clear anisotropy in the orbital torque generation efficiency depending on the direction of the applied electric field, consistent with the calculations. Furthermore, when using this orbital torque to reverse the magnetization of Ni, we found that the critical current density required for magnetization switching also varied according to the magnitude of the orbital torque generation efficiency. In this way, our study discusses the anisotropy of the orbital Hall effect in epitaxial transition metals with an aspect not observed in previously reported polycrystalline systems and offers a new direction in research on the orbital Hall effect.

Grain boundaries are critical for determining the functionality of polycrystalline materials. Here we investigate and present the structural and transport properties of grain boundaries in the unconventional superconductor ${\mathrm{CeCoIn}}_5$. We provide a detailed recipe for the fabrication of isolated grain-boundary devices from as-grown polycrystalline samples of ${\mathrm{CeCoIn}}_5$. Electron backscattered diffraction imaging of polycrystalline ${\mathrm{CeCoIn}}_5$ samples reveals an abundance of ${90}^{\circ }$ misorientation grain boundaries, suggesting a preferential nucleation of ${\mathrm{CeCoIn}}_5$ grains with ${90}^{\circ }$ misorientation over a random distribution of grain orientations. Transport measurements across grain-boundary devices establish coherence of superconductivity and allow us to establish a lower bound on the critical current density for the grain boundaries. Our work opens possibilities for fabrication of quantum devices such as Josephson junctions out of bulk unconventional superconducting materials.

We successfully synthesized single crystals of a series of C15b Laves-phase compounds, $R{\mathrm{InCo}}_4$ ($R=\mathrm{Dy}–\mathrm{Tm}$), with Co-pyrochlore and $R$-fcc sublattices, and systematically studied their magnetic properties via magnetometry measurements. These itinerant cubic compounds, with Curie temperatures above room temperature, show compensated ferrimagnetism featuring an antiferromagnetic coupling between the two sublattices. From this series, ${\mathrm{DyInCo}}_4$ exhibits the highest $T_{\mathrm{C}}(=368\mathrm{K}$) and a near-room-temperature compensation point $T_{\mathrm{cp}}(=295\mathrm{K}$). $T_{\mathrm{C}}$ does not change drastically with the $R$ atom, whereas $T_{\mathrm{cp}}$ is dependent. Another magnetization anomaly is observed in all the compounds at low temperatures, which may be indicative of changes in the lattice or magnetic structure. The easy axis of the ferrimagnetic moment of ${\mathrm{DyInCo}}_4, {\mathrm{ErInCo}}_4$, and ${\mathrm{TmInCo}}_4$ is proposed at $T=5\mathrm{K}$ to be along the [001], [111], and [110] directions, respectively. However, the simple easy-axis or easy-plane ferrimagnetic picture cannot be applied to ${\mathrm{HoInCo}}_4$. These observations suggest that the $R$ sublattice determines magnetic anisotropy and compensation, while the Co sublattice plays a role in strong magnetic ordering. The high Curie temperature, together with the magnetization compensation point near room temperature, renders these itinerant pyrochlore magnets interesting for spintronic applications.