We report the development of ferromagnetic nematic colloids using a two-step protocol tailored for investigating emergent magnetoelastic phenomena. First, we prepared a ferromagnetic nematic liquid crystal by dispersing well-defined magnetic nanoparticles into a conventional nematic host, ensuring magnetic ordering while preserving the characteristic director field. Subsequently, microparticles were suspended within this ferromagnetic nematic matrix that generates elastic dipoles and quadrupoles in the director field. We show that a slowly rotating magnetic field induces surface domain $\pi$ walls that quasistatically reorient the defects and linear colloidal assemblies—an effect that is absent in ordinary nematic liquid crystals lacking spontaneous magnetization. The results are interpreted using the Landau–de Gennes Q-tensor model, extended to capture the coupling between nematic and magnetic characteristics of ferromagnetic nematic liquid crystals. This composite system enables the exploration of novel elastic and magneto-optic interactions at the interface of liquid crystalline order and nanoscale magnetism, broadening the experimental landscape for both fundamental studies and potential applications in adaptive materials that involve colloidal composites.

While ultrasonication is a well established method to disperse nanorods, insufficient attention has been given to the impact of the particle mass fraction $W_s$ at which sonication takes place. Its importance goes far beyond viscosity tuning, since a dilute isotropic nanorod suspension transitions to a liquid crystal (LC) phase if $W_s$ surpasses a threshold, via a wide biphasic window of isotropic–LC equilibrium phase coexistence. By systematically varying $W_s$ of suspensions of cellulose nanocrystals (CNCs) across and beyond the biphasic range we show that $W_s$ strongly influences the sonication process. Near the original suspension's stability limit of the isotropic phase, $W_0^{*}$, the sonication shear flow induces a temporarily ordered paranematic state which assists particle individualization and minimizes damage. Our atomic force microscopy study supports this, finding increasing aspect ratio nanorods as $W_s$ is increased from the fully isotropic range past the onset of the equilibrium biphasic window. $W_s$ impacts also the macroscopic properties like the phase diagram and the pitch of the cholesteric LC helix into which CNCs self-assemble. A further key finding is that CNC suspensions concentrated beyond the threshold for gelation should be sonicated to remove end-to-end chains formed in the gel, since otherwise these remain even after dilution. Our conclusions apply also to many other nanorod, nanotube and nanoplatelet suspensions, where reproducibility problems may be due to the lack of control of $W_s$ and to agglomerates remaining from high-concentration precursor suspensions.

Here, we propose a comprehensive first-principles atomistic approach to predict the Wulff-Kaischew equilibrium shape of crystals heterogeneously integrated on a dissimilar material. This method uses both reconstructed surface and interface absolute energies, as determined by density functional theory, to infer the morphology and wetting properties of Volmer-Weber islands over the whole range of accessible chemical potentials. The predicted equilibrium shapes of GaP crystals heterogeneously grown on Si are found to be in good agreement with experimental observations performed by transmission electron microscopy. This method provides a tool for optimization of heterostructured, multifunctional, and smart materials and devices.

We propose and theoretically demonstrate a platform for realizing both the axion insulator and quantum anomalous Hall (QAH) phases. This platform is a ${\mathrm{Bi}}_2{\mathrm{Se}}_3$-based topological insulator film that is confined between two out-of-plane magnetized films of ${\mathrm{MnBi}}_2{\mathrm{Se}}_4$ and ${\mathrm{CrBi}}_2{\mathrm{Se}}_4$. Our first-principles calculations show that this design induces substantial splitting of the topological surface states which facilitates the realization of axion and QAH phases at elevated temperatures. This work establishes a tunable material platform for probing the interplay between distinct topological magnetic phases and for exploiting their exotic properties in next-generation devices.

We report the anisotropic magnetization and the anomalous Hall effect (AHE) in single-crystalline ${\mathrm{AlFe}}_2{\mathrm{B}}_2$, which undergoes a ferromagnetic (FM) transition at 275 K. The intrinsic mechanism is essential for the AHE in the FM state, resulting in a significant anomalous Hall conductivity of over 200 ${\mathrm{\Omega }}^{-1}{\mathrm{cm}}^{-1}$ at low temperatures. Due to its moderate susceptibility as a soft magnet, this material exhibits a high resistivity sensitivity across a wide temperature range, suggesting its potential as an anomalous Hall sensor for detecting weak magnetic fields.

The role of environmental water in graphite lubrication has generated conflicting observations and considerable confusion. Early hypotheses suggested water intercalation between graphene layers, but x-ray diffraction studies revealed no change in interlayer spacing with changing humidity. Conversely, recent Raman spectroscopy studies indicated water intercalation in bilayer graphene under humid conditions. To reconcile these discrepancies, we report density functional theory (DFT) and molecular dynamics (MD) simulations coupled with a reinterpretation of experimental measurements. While DFT calculations reveal softer surface interlayers suggesting potential for water intercalation, MD simulations indicate that such intercalation requires a significant reduction in van der Waals interactions, beyond what surface-induced softening can achieve. Alternatively, if water does intercalate, it likely occurs between the surface layers where graphene interactions are over 80% weaker than in bulk graphite, making such intercalation plausible. Instead, we demonstrate that water forms clusters on the graphene surface, maintaining a stable two-atomic layer structure across a wide temperature range, emphasizing the importance of surface water adsorption. We therefore propose that the lubrication effect is primarily related to the graphene-water interface rather than the graphene-graphene interface. While we do not completely rule out water intercalation, our findings suggest that graphene-water interactions dominate lubrication. These results resolve previous discrepancies by highlighting the role of surface or near-surface water layers over bulk intercalation, underscoring the significance of molecular interactions at the graphene-water interface in confined nanoscale spaces.

The efficacy of single-site defect engineering in graphitic carbon nitride ($\mathrm{g}-{\mathrm{C}}_3{\mathrm{N}}_4$) is often compromised by the inevitable creation of charge recombination centers. To overcome this limitation, we propose a synergistic dual-site defect strategy and develop a high-pressure and high-temperature (HPHT) method to concurrently introduce oxygen dopants and nitrogen vacancies into $\mathrm{g}-{\mathrm{C}}_3{\mathrm{N}}_4$. During HPHT treatment, adsorbed oxygen atoms are embedded into the lattice, while adjacent nitrogen atoms are expelled to form vacancies. Such dual-defects induce slight band-gap narrowing of $\mathrm{g}-{\mathrm{C}}_3{\mathrm{N}}_4$ while significantly promote charge transfer and separation, thereby boosting photocatalytic hydrogen evolution. Theoretical calculations confirm that the oxygen dopants (p-type doping) and nitrogen vacancies (n-type doping) act as donor-acceptor pairs. This charge compensation effect prevents the formation of localized impurity states in the gap but instead modifies the band edges to enhance the oxidation capability and facilitate the spatial separation of electron and hole carriers. Benefiting from these advantages, the optimized $\mathrm{g}-{\mathrm{C}}_3{\mathrm{N}}_4$ exhibits a twofold enhancement in photocatalytic activity, accompanied by a marked increase in carrier concentration. This work provides a novel strategy and fundamental insights for synthesizing highly efficient defect-engineered photocatalysts.

Borophene, a unique two-dimensional boron-based material with a graphenelike structure, has attracted growing interest due to its special configurations and remarkable physical and chemical properties. This study focuses on four different borophene phases: $\alpha , \beta 12, \gamma 3$, and trigonal, and systematically investigates their hydrogen evolution reaction (HER) performance. By using density functional theory (DFT), we evaluate the intrinsic catalytic activity of freestanding borophene monolayers as well as the influence of an Ag(111) substrate on their HER behavior. The results indicate that the freestanding $\alpha , \beta 12$, and $\gamma 3$ phases exhibit excellent HER activity, characterized by optimal Gibbs free energies for hydrogen adsorption. Especially, the on-top site with the lowest coordination number is identified as the most active site. However, interaction with the Ag(111) support significantly modifies the hydrogen binding, leading to suppressed HER performance in these phases. In contrast, the trigonal phase displays relatively poor HER performance, attributed to its fully saturated bonding environment, while the silver substrate significantly modifies its geometric configuration and slightly enhances the HER performance. This work highlights both the promising intrinsic HER potential of borophene monolayers and the critical impact of substrate interactions, guiding the design of efficient borophene-based electrocatalysts.

A quantitative measure of symmetry breaking is introduced that allows the quantification of which symmetries are most strongly broken due to the introduction of some kind of defect in a perfect structure. The method uses a statistical approach based on the Jensen-Shannon divergence. The measure is calculated by comparing the transformed atomic density function with its original. Software code is presented that carries the calculations out numerically using Monte Carlo methods. The behavior of this symmetry breaking measure is tested for various cases including finite size crystallites (where the surfaces break the crystallographic symmetry), atomic displacements from high symmetry positions, and collective motions of atoms due to rotations of rigid octahedra. The approach provides a powerful tool for assessing local symmetry breaking and offers new insights that can help researchers understand how different structural distortions affect different symmetry operations.

Field evaporation in atom probe tomography (APT) includes known processes related to surface migration of atoms, such as the so-called roll-up mechanism. They lead to trajectory aberrations and artifacts on the detector. These processes are usually neglected in simulations. The inclusion of such processes is crucial for providing reliable models for the development and verification of APT reconstruction algorithms, a key part of the whole methodology. Here, we include stochastic lateral velocity perturbations and a roll-up mechanism to simulations performed using the Robin-Rolland model. By comparing with experimental data from Al and Ni systems, we find the stochastic perturbation energy distributions that allow us to very accurately reproduce the detector patterns seen experimentally and thus greatly improve the accuracy of the simulations. We also explore the possible causes of remaining discrepancies between the experimental and simulated detector patterns.

High power consumption, leakage currents, and fatigue in conventional electrical switches motivate the development of alternative switching paradigms for low-power and high-contrast signal control. In this study, a twisted bilayer SnTe switching architecture based on interlayer-twist-induced polarization switching is proposed. Introducing a finite twist disrupts the intrinsic symmetry of few-layer α-SnTe, generating an out-of-plane polarization and enabling a large-contrast switching response. Near a twist angle of $27.8^{\circ }$, with a gradual rotation of $0.{323}^{\circ }$, the polarization undergoes a pronounced evolution from a virtually negligible value to a maximum of $3.26\times {10}^{-11}\mathrm{C}/\mathrm{m}$, with the polarization differing by $3.24\times {10}^{-11}\mathrm{C}/\mathrm{m}$ between the two stable states. The remarkable polarization response induced by the subdegree interlayer twist establishes a viable strategy for designing low-power logic devices and multifunctional quantum electronic systems at the nanoscale.

We report on the epitaxial growth of nm-thick films of bismuth-substituted yttrium iron garnet (BiYIG) by high-temperature off-axis radio-frequency magnetron sputtering. We demonstrate accurate control of the magnetic properties by tuning of the sputtering parameters and epitaxial strain on various (111)-oriented garnet substrates. BiYIG films with up to −0.80% lattice mismatch with the substrate remain fully strained up to 60 nm thick, maintaining a high crystalline quality. Transmission electron microscopy and energy-dispersive x-ray spectroscopy confirm coherent epitaxial growth, the absence of defects, and limited interdiffusion at the BiYIG/substrate interface. Varying the tensile or compressive strain between −0.80% and $+0.56\%$ in BiYIG allows for accurate compensation of the total magnetic anisotropy through magnetoelastic coupling. The effective magnetic anisotropy of sputtered BiYIG films can be further tuned via the off-axis deposition angle and the oxygen flow during growth, which determine the cation stoichiometry. Under optimized growth conditions, a ferromagnetic resonance (FMR) linewidth of 1 mT at 10 GHz is reliably obtained even for thicknesses as low as 10 nm. We also report small FMR linewidths in ultrathin (2–5 nm) BiYIG films grown on diamagnetic substrate yttrium scandium gallium garnet. These findings highlight the promise of low-damping, strain-engineered nm-thick BiYIG films for implementing advanced functionalities in spin-orbitronic and magnonic devices. Specifically, the magnetic-anisotropy compensation and low damping enable large cone-angle magnetization dynamics immune to magnon-magnon nonlinear scattering.

We report a method to grow B20 MnGe thin films using molecular-beam epitaxy, which employs an ultrathin CrSi template layer on Si(111). This layer is expected to be nonmagnetic, in contrast to MnSi and FeGe buffer layers that have been used previously. This template layer permits an investigation of the intrinsic properties of MnGe in the ultrathin-film limit without the influence of a neighboring magnetic layer. Single-phase MnGe(111) films were grown with thicknesses between 2 and $40\mathrm{n}\mathrm{m}$, which exhibited low interfacial roughnesses on the order of $0.6\mathrm{n}\mathrm{m}$. The films crystallized in a B20 structure with a small rhombohedral distortion. Magnetometry measurements in out-of-plane fields are consistent with a cone phase derived from helimagnetic order propagating along the film normal. However, an unexpected remanent moment develops below $35\mathrm{K}$, concomitant with features in the field dependence of the transport data. This provides indirect evidence for the presence of a low-temperature phase which has been identified by others as either a triple-$Q$ topological spin-hedgehog lattice, or a multidomain single-$Q$ helical state.

Strontium iron oxide undergoes a voltage-driven topotactic phase transition between an insulating brownmillerite (BM) and a conductive perovskite (PV) structure. Understanding this redox-based transition requires, first, a detailed characterization of and, second, a detailed description of field-driven oxide-ion transport in both phases. In this study, we used classical molecular dynamics (MD) simulations to determine the oxide-ion mobility $u_{\mathrm{O}}$ in anisotropic ${\mathrm{Sr}}_2{\mathrm{Fe}}_2{\mathrm{O}}_{5\pm \delta }$ (BM phase) and in isotropic ${\mathrm{SrFeO}}_{2.5\pm \delta /2}$ (PV phase) as a function of electric field strength, $0.5\le E/\mathrm{M}\mathrm{V}\mathrm{c}{\mathrm{m}}^{-1}\le 10$, and as a function of temperature, $1300\le T/\mathrm{K}\le 3000$. The use of oxygen-excess ($+\delta$) and oxygen-deficient ($-\delta$) BM systems permits, respectively, interstitialcy and interstitial migration, and vacancy migration, to be probed. From $u_{\mathrm{O}}$ results obtained at low fields (i.e., within the linear regime), we obtain the activation enthalpies and effective attempt frequencies of oxygen-vacancy migration and oxygen-interstitial/oxygen-interstitialcy migration; and, together with literature data for tracer diffusivities, we determine Haven ratios $H_{\mathrm{r}}\left(T\right)$ for BM and PV phases. At higher fields (i.e., within the nonlinear regime), $u_{\mathrm{O}}\left(E\right)$ data shows a strong nonlinear response for all three migration mechanisms. In each case, the behavior is described within an existing analytical framework that uses as input the zero-field activation enthalpies and effective attempt frequencies. Interstitialcy migration displays a stronger nonlinear response compared with interstitial or vacancy migration, and this is ascribed to its longer effective charge displacement arising from its collective nature. Finally, the MD simulations at high field strengths indicate a field-driven BM-to-PV phase transition (at constant oxygen stoichiometry).

Brittle or ductile failure of materials is typically governed by a competition between crack propagation and plastic deformation. For ductile crystals like aluminum, this framework shows that brittle fracture does not occur, regardless of preexisting cracks. However, it does not account for environmental effects that can promote embrittlement. We show that self-assembled organic monolayer adsorbates of varying chain length can induce a ductile-to-brittle transition in crystals under bending and shear. These adsorbates impose a surface stress that varies from compressive to tensile with increasing chain length, driving the transition. We develop an analytical model incorporating adsorbate-induced surface stress into the criterion for dislocation emission and compare it against crack propagation. This yields an embrittlement map demarcating regimes of ductile and brittle behavior in load-surface stress space. Our findings suggest a critical role for surface stress in environmentally assisted cracking, as well as opportunities for utilizing this stress to enhance manufacturing processes such as machining, polishing, and comminution.

This research establishes a systematic, high-throughput computational framework for designing radiation-resistant, dilute ternary copper-based alloys by addition of solutes that bind to vacancies and reduce their mobility, thus promoting interstitial-vacancy recombination. The first challenge in developing alloys by this method is mitigating the vacancy-mediated solute drag effect, since density functional theory (DFT) calculations show that solutes that bind strongly to vacancies are also rapidly dragged to point-defect sinks, and thus removed from the matrix. To overcome this problem, two types of solutes are added to the Cu matrix: a first solute with a strong vacancy binding energy ($B$-type species) and another solute that binds to ‘‘B’’ and is a slow diffuser in Cu ($C$-type species). Using DFT, 21 synergistic solute pairs are screened, with “B”$=\mathrm{Zr}$, Ge, Sn and “C”$=\mathrm{Fe}$, Co, Mo, Ni, Nb, W, Cr. Two promising alloys, Cu(Zr,Co) and Cu(Zr,Fe) are then investigated in detail in the dilute regime. Diffusion and solute drag in these alloys are modeled using the kinetic cluster expansion approach (KineCluE) under irradiation conditions. It is shown that strong Zr-‘‘C’’ thermodynamic binding, especially between Zr and Co, significantly reduces the mobility of Zr solute and suppresses the vacancy-mediated solute drag. Using an analytical framework for the standard five-jump frequency model for diffusion in binary alloys, it is found that vacancy-Zr-Co triplets disrupt the kinetic circuits that promote solute drag in the binary alloy by raising the dissociation barrier for the vacancy from the solute.

The stability of Fe-Si compounds under extreme pressure is critical for understanding the composition and evolution of Earth's core and terrestrial planetary interiors. Using first-principles calculations and adaptive genetic algorithm crystal structure prediction method, we systematically investigated the thermodynamic stability of Fe-Si compounds and their structural evolution as a function of silicon concentration over pressures ranging from 0 GPa to 1 TPa. At 0 K, B2-FeSi is identified as the sole thermodynamically stable phase at high pressures. Through structural characterization analysis of metastable structures, we found that as the Si content increases, there is a transition in structural motifs from hcp to bcc and then to fcc. Furthermore, electronic and vibrational entropies significantly enhance the thermodynamic stability of certain alloy structures. Our study highlights the synergistic effects of composition, pressure, and volume in regulating phase stability, providing theoretical insights into the composition and structural evolution of planetary cores.

$\mathrm{HfZr}{\mathrm{O}}_2$(HZO) is a promising ferroelectric material compatible with CMOS technology, retaining functionality at nanometer-scale thicknesses. Its ferroelectricity arises from metastable polar phases—orthorhombic ($Pca{2}_1$) and rhombohedral (R3m)–coexisting with the thermodynamically stable, non-polar monoclinic phase ($P{2}_1/c$). Accurate quantification of these coexisting phases is essential for optimizing device performance. Here, we use first-principles calculations to estimate core-level shifts in the O 1s X-ray photoelectron spectroscopy (XPS) peak, revealing a distinct, up to 0.84 eV higher binding energy component for oxygen atoms in the polar sublattice compared to those in non-polar environments. These shifts incorporate both initial and final state effects in photoemission. Experimental validation through X-ray diffraction (XRD) and XPS on HZO films with varying phase composition confirms our predictions. Our findings provide a clear, spectroscopically accessible fingerprint to distinguish polar and non-polar phases in HZO via O 1s XPS analysis, offering a practical tool for phase quantification and enabling targeted integration of ferroelectricity in advanced nanoelectronic devices.