Crystal structure prediction (CSP) is crucial for identifying stable crystal structures in given systems and is a prerequisite for computational atomistic simulations. Recent advances in neural network potentials (NNPs) have reduced the computational cost of CSP. However, searching for stable crystal structures across the entire composition space in multicomponent systems remains a significant challenge. Here, we propose an improvement of a genetic algorithm (GA)-based CSP method using a universal NNP designed to efficiently expand convex hull volumes while preserving the diversity of crystal structures. Our hull-informed filtering and elitist-selection procedures incorporate an aging mechanism that prioritizes recently improved compositions. We also employ niching to prevent convergence to a small set of stoichiometries, thereby preserving a diverse, high-quality population. Our evaluation shows that the present method outperforms the symmetry-aware random structure generation and existing CSP methods, achieving a larger convex hull with fewer trials. We demonstrated that our approach, combined with the developed universal NNP (PFP), can accurately reproduce and explore phase diagrams obtained through DFT calculations; this indicates the validity of PFP across a wide range of crystal structures and element combinations. This study, which integrates a universal NNP with a GA-based CSP method, highlights the promise of these methods in materials discovery.

Understanding the structure–property relationships in layered transition-metal carbides or nitrides, known as MXenes, is of critical importance for their rational design, synthesis, and application. However, the vast chemical and structural diversity of MXenes, stemming from their wide range of M and X elements, surface terminations, and different atomic coordination environments, makes it challenging to clearly understand these structure–property relationships. In this work, we perform first-principles density functional theory (DFT) calculations and molecular dynamics (MD) simulations to comprehensively investigate the stability and a variety of physical properties of MXenes with different coordination environments. Using Ti- and Mo-based carbide MXenes as model systems, energetic calculations reveal that Ti-based MXenes are most stable in octahedral coordination, whereas Mo-based MXenes preferentially adopt prismatic coordination. This fundamental difference in preferred atomic coordination gives rise to markedly distinct properties between these two systems as a function of the fraction of octahedral and prismatic sites. For instance, the in-plane stiffness of Ti-based MXenes increases as octahedral coordination becomes dominant, but it decreases in the Mo-based MXenes under the same conditions. Additional stability analyses based on mechanical, lattice-dynamical, and temperature-dependent thermodynamic properties demonstrate that many metastable MXenes not only satisfy the strict stability criteria but can also undergo phase transitions among different structures and even become stabilized at elevated temperatures. Although surface terminations, such as F and O atoms, do not alter the energetic ordering or the overall stiffness trends among stable and metastable MXenes, they influence other material properties. For instance, O termination can induce semiconducting behavior in both stable and metastable ${\mathrm{Ti}}_2{\mathrm{CO}}_2$ MXenes. This study significantly advances the fundamental understanding of structure–property relationships in MXenes and provides valuable guidance for developing coordination-based design principles to precisely engineer MXenes with improved properties.

Spin-orbit torque (SOT) magnetoresistive random-access memory (MRAM), a nonvolatile memory technology, exhibits promising prospects for advancing memory devices. However, it still faces pivotal challenges in achieving high SOT efficiency and realizing deterministic field-free switching in perpendicular magnetization SOT devices. Herein, we propose an effective strategy to realize high-efficiency field-free switching with an ultralow critical current density $(J_{\mathrm{c}}=3.9$ $\mathrm{MA}/\mathrm{c}{\mathrm{m}}^2)$ by doping copper (Cu) into the topological insulator (TI) ${\mathrm{Bi}}_{0.9}{\mathrm{Sb}}_{0.1}$ (BiSb). The cosputtered Cu-BiSb alloy film achieves a high conventional transverse spin polarization efficiency $({\xi }_{\mathrm{y},\mathrm{DL}}=0.53)$. In contrast to undoped BiSb, it exhibits a significant fieldlike torque induced by spin currents with out-of-plane spin polarization $({\xi }_{\mathrm{z},\mathrm{FL}}=0.55)$. This unconventional spin polarization enables deterministic field-free switching of perpendicular magnetization with as low as $J_{\mathrm{c}}\sim 4$ $\mathrm{MA}/\mathrm{c}{\mathrm{m}}^2$ in Cu-BiSb/Pt/Co/Pt heterostructures. Our work provides critical support for the development of TI-based, high-performance, and integrable SOT-MRAM devices.

Over the past decade, there has been steady research on superconducting junctions with a ferromagnet as the weak link and where triplet correlations can transport supercurrents over a substantial distances. Of particular interest are half-metallic ferromagnets, in which only one spin band is present, so that, presumably, the induced supercurrent is fully spin polarized. We have earlier reported on a study of triplet transport in planar ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_3\left(\mathrm{LSMO}\right)$ nanostrip Josephson junctions with NbTi superconducting contacts, where we found high values for the supercurrents, and large junction lengths (up to 1.3 µm). Here we extend that work by studying the dependence of the critical current $I_c$ on the length of the nanostrip between the contacts and the width of the strip. All junctions show strong supercurrents, but we do not observe simple systematics. Apparently, the fabrication process does not allow sufficient control over some of its parameters. To gain more insight in the mechanism for triplet generation at the LSMO/NbTi interface, we also studied the effect of Pt as an interlayer between the LSMO and the NbTi. For this, we etched a NbTi/Pt electrode structure on a full film of LSMO. The results are highly promising, showing sharp superconducting transitions and zero-resistance states being reached at an electrode distance of 2 µm, with indications that larger distances should be feasible.

First-principles studies were performed on two Mn-based ferrimagnetic Heusler compounds with $L{2}_1$ and $B2$ structures, that is, ${\mathrm{Mn}}_2\mathrm{V}\mathit{Z}$ ($\mathit{Z}=\mathrm{Al}$ or Ga). The aim was to investigate their magnetic properties, electronic structures, and spin-resolved longitudinal conductivity at both zero and elevated temperatures. Density functional theory and functional integral theory were used. This approach incorporates transverse spin fluctuations through a disordered local moment method and the coherent potential approximation. In most cases, the calculated theoretical Curie temperatures were lower than the experimental values. Alloys with a $B2$ structure exhibit higher Curie temperatures compared to compounds with an $L{2}_1$ structure. Calculations of the temperature dependence of the density of states (DOS) indicate that the half-metallic electronic structure collapses due to self-energy effects that reflect spin disorder at nonzero temperature. In other words, transverse spin fluctuations are renormalized in the electronic structure. However, the spin-resolved longitudinal conductivities demonstrated an improved spin polarization, particularly for ${\mathrm{Mn}}_2\mathrm{VGa}$ with an $L{2}_1$ structure. The competition between the half-metal-to-normal-metal transitions, which are caused by a modification of the DOS, and scattering coming from spin-disorder explains this behavior of conductivities. Both of these effects are induced by transverse spin fluctuations. Additionally, the results show that the spin polarizations defined in terms of the conductivities and of the DOS do not follow the same trends at $T>0$. Their temperature dependencies are not the same, particularly for the $L{2}_1$ structures, although they are related to each other. Finally, the total energy landscape of the paramagnetic state was calculated using the fixed spin moment method to investigate the strength of the longitudinal spin fluctuations. These results suggest that the alloys may exhibit strong longitudinal spin fluctuations.

The discovery of filling-controlled phase modulations in correlated systems opens an emerging paradigm to unlock unique electromagnetic states and physical phenomena, transcending traditional paradigms. Here, correlated $\mathrm{V}{\mathrm{O}}_2$ (B) is selected as a model system to realize multiple electronic phase modulations through ionic evolution, leveraging the inherent ${\mathrm{V}}_4{\mathrm{O}}_{10}$-type double-layered structure and thermodynamic metastability. The introduction of electron carriers into the $\mathrm{V}-3d$ orbital of metastable $\mathrm{V}{\mathrm{O}}_2$ (B), as driven by ${\mathrm{W}}^{6+}$ substitution, oxygen deficiency, or protonation, triggers the carrier delocalization, giving rise to sequential electronic phase modulations, beyond well-established M1 and R phases of $\mathrm{V}{\mathrm{O}}_2$. Of particular note is the synergistic interplay between oxygen defects and interstitial protons in cooperatively driving electronic state evolutions in $\mathrm{V}{\mathrm{O}}_2$ (B) through band-filling regulation, enabling the robust control over the energy landscape in a reversible pathway. Utilizing synchrotron-related spectroscopy techniques and theoretical calculations, we reveal that the band filling in low-energy ${\pi }^{*}$ orbital of $\mathrm{V}{\mathrm{O}}_2$ (B) through electron doping governs electronic phase modulations, delivering a unified physical picture. Our findings not only demonstrate a powerful tuning knob for adjusting correlated electronic states in metastable layered-structure materials, fostering exotic physical functionalities and phenomena but also extend the horizons in materials designs for iontronic device applications.

Among all-inorganic halide perovskites, the only known ferroelectrics are the family of ${\mathrm{CsGeX}}_3$ (X = Cl, Br, I). Here, we study their ferroelectric domain walls (DWs) and common point defects by density functional theory (DFT) calculations and investigate the interplay between DWs and defects. The most stable defects are ${\mathrm{V}}_{\text{X}}$ and ${\mathrm{V}}_{\text{Cs}}$ and the former shows low migration barriers and high mobility. In contrast to oxide ferroelectrics, the affinity between point defects and DWs is negligible, reflecting the subtle structural distortions at ${\mathrm{CsGeX}}_3$ DWs. Concomitantly, the formation energies and migration energy barriers of ${\mathrm{CsGeX}}_3$ DWs are small compared to oxides, and neither ${\mathrm{V}}_{\text{X}}$ nor ${\mathrm{V}}_{\text{Cs}}$ pin migrating DWs. The band-gap invariance across DWs and the lack of affinity towards intrinsic charged-point defects imply that conducting DWs for nanoelectronics may be challenging to realize in ${\mathrm{CsGeX}}_3$. However, shallow $p$-type defect levels and low-hole effective masses suggest that high $p$-type conductivity may be achievable in nominally ferroelectric ${\mathrm{CsGeX}}_3$. The low DW migration energy barriers and insignificant DW pinning by point defects make ${\mathrm{CsGeX}}_3$ promising materials as robust soft ferroelectrics for high-frequency switching applications with low energy dissipation.

Rotational magnetocaloric effect (RMCE) is achieved by simply rotating magnetic material in a constant magnetic field, offering a simpler and more efficient method for magnetic refrigeration compared to conventional methods. In general, strong magnetic anisotropy is required to obtain sizable RMCE, explaining why in-plane RMCE is rarely observed in thin films due to the usually weak in-plane magnetic anisotropy. In this work, we demonstrate that pronounced in-plane magnetic anisotropy can be achieved by controlling the shape of electronic phase separation ferromagnetic regions in $\mathrm{L}{\mathrm{a}}_{0.425}\mathrm{P}{\mathrm{r}}_{0.2}\mathrm{C}{\mathrm{a}}_{0.375}\mathrm{Mn}{\mathrm{O}}_3$ thin films grown on (001) $\mathrm{NdGa}{\mathrm{O}}_3$ substrates. Isothermal magnetization measurements reveal that the system exhibits an in-plane rotating entropy change $-\mathrm{\Delta }{S}_{\mathrm{rot}}=1.77\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$ near $T_{\mathrm{C}}\approx 155$ K with relative cooling power of 23.78 $\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}$. The successful realization of such sizable in-plane RMCE is important for chip-integrated solid-state refrigeration for microelectronic and spintronic platforms.

A better understanding of the mechanisms of vacancy clustering and diffusion in concentrated solid solutions is essential to improve the design of alloys with enhanced radiation tolerance and thermal stability. In this study, the kinetic activation-relaxation technique (kART) was employed to investigate vacancy cluster behavior in FeNiCr CSAs at the atomistic level. By analyzing di-, tri-, and tetravacancy clusters, we reveal that cluster stability increases with size, driven by reduced formation energies, while local chemical composition—particularly Ni's stabilizing effect and Cr's role in enhancing mobility—influences defect evolution. By computing the diffusion barriers and entropic prefactors for more than 700 000 diffusion events, we find that divacancies combine notable stability with substantial mobility, while trivacancies exhibit significant mobility despite reduced stability, enabling efficient defect recombination through short-range migration mechanisms. In contrast, tetravacancies demonstrate greater stability but significantly restricted mobility, influencing localized defect interactions and microstructural evolution. These findings provide fundamental insights into the complex interplay between cluster size and local composition that affect both the enthalpic and entropic contributions to diffusion kinetics, offering a predictive framework for rationally designing alloy compositions to optimize radiation resistance and structural integrity in advanced nuclear and aerospace applications.

The brittleness or ductility of metals has long been attributed to their elastic constants, with a high Poisson ratio, or equivalently, a high Pugh ratio, favoring greater ductility. Growing evidence links ductility with their electronic structure. Consequently, it is desirable to understand how the electronic structure affects the elastic constants. Here, we examine the Ta-W binary alloy system, which evolves from ductile character at Ta-rich compositions to brittleness at high W. We show that a change in slope of the composition-dependent shear modulus near the equiatomic composition coincides with an abrupt change in the Fermi level density of states. We relate the behaviors of the elastic constants to the characters of occupied electronic orbitals close to the Fermi level. Finally, we consider additional alloy systems from groups V and VI and show that qualitatively similar behavior occurs more broadly.

The quasi-one-dimensional diamond spin chain systems have attracted significant research attention for unveiling novel quantum magnetic phenomena driven by low dimensionality and magnetic frustration. Even though several $3d$ transition-metal (TM)-based diamond chain magnets have been studied, rare-earth (RE) counterparts are still rare. Herein, we report a family of rare-earth diamond chain compounds, $\mathrm{NaB}{\mathrm{a}}_3\mathrm{R}{\mathrm{E}}_3\mathrm{S}{\mathrm{i}}_6{\mathrm{O}}_{20}$ ($\mathrm{RE}=\mathrm{Nd}$, Gd-Dy), which crystallize in an orthorhombic structure with the Ama2 space group. The structural analysis reveals that the edge-sharing ${\mathrm{REO}}_8/{\mathrm{REO}}_7$ polyhedra form an infinite diamond chain along the $c$ axis with well separation by the nonmagnetic ${\mathrm{SiO}}_4$ tetrahedra and ${\mathrm{BaO}}_7/{\mathrm{BaO}}_8$ polyhedra perpendicular to the $c$-axis, in which the nearest neighboring (NN) intra-chain RE-RE distance $d_{\mathrm{intra}}\sim 3.818-3.916\AA$ is significantly shorter than the NN inter-chain distance $d_{\mathrm{inter}}\sim 6.471-6.763\AA$. Magnetic measurements indicate no magnetic order down to 1.8 K for all family members. Specific heat characterizations on ${\mathrm{NaBa}}_3{\mathrm{Nd}}_3{\mathrm{Si}}_6{\mathrm{O}}_{20}$ and ${\mathrm{NaBa}}_3{\mathrm{Gd}}_3{\mathrm{Si}}_6{\mathrm{O}}_{20}$ reveal the formation of long-range magnetic order at $T_{\mathrm{N}}\sim 0.20$ K and $T_{\mathrm{N}}\sim 0.42$ K with large spin fluctuations at low temperatures. Furthermore, ${\mathrm{NaBa}}_3{\mathrm{Gd}}_3{\mathrm{Si}}_6{\mathrm{O}}_{20}$ exhibits a large magnetocaloric effect at temperatures below 1 K, making it an attractive candidate for sub-Kelvin magnetic refrigeration. The serial family compounds $\mathrm{NaB}{\mathrm{a}}_3\mathrm{R}{\mathrm{E}}_3\mathrm{S}{\mathrm{i}}_6{\mathrm{O}}_{20}$ provide an ideal platform for exploring novel diamond spin chain physics involving $4f$ electrons.

Chemical composition provides a powerful route to tune the electronic ground state of iron-based superconductors and other quantum materials, yet access to highly doped phases remains limited. Here we demonstrate that high-pressure thermal decomposition of hydrogen-rich precursors enables overhydrogenation of LaFeSi. Using anthracene, we synthesize tetragonal superconducting LaFeSiH, including a single hydrogen site, while ammonia borane yields a structurally distorted overhydrogenated phase, ${\mathrm{LaFeSiH}}_{1+x}$, with an orthorhombic structure. Chemical analysis reveals excess hydrogen ($x\approx$ 0.6), implying a second H site in ${\mathrm{LaFeSiH}}_{1.6}$ whose localization and occupancy are determined by neutron diffraction. In contrast to metallic LaFeSi and superconducting LaFeSiH, orthorhombic ${\mathrm{LaFeSiH}}_{1.6}$ exhibits semiconductorlike behavior. Upon hydrogen release near 100 °C, it transforms into tetragonal superconducting ${\mathrm{LaFeSiH}}_{1+\delta }$ ($\delta \ll 0.6$). These results establish the chemical flexibility of the layered $\mathrm{LaFeSi}X$ ($X$ = H, O, F) family and provide access to a high hydrogen-doping regime, creating new opportunities to investigate superconductivity in Fe-based silicides.

$A$-site-ordered perovskites ($A{A^{\prime }}_3{B}_4{\mathrm{O}}_{12}$) provide a structurally robust platform for exploring correlated-electron behavior, offering unusual opportunities to disentangle the roles of orbital degrees of freedom, bonding interactions, and local structural distortions. In this work, we synthesize a new $A$-site-ordered perovskite $\mathrm{PbC}{\mathrm{u}}_3{\mathrm{V}}_4{\mathrm{O}}_{12}$ under high-pressure and high-temperature conditions and perform comprehensive structural and physical characterizations. $\mathrm{PbC}{\mathrm{u}}_3{\mathrm{V}}_4{\mathrm{O}}_{12}$ crystallizes in the cubic $\mathit{Im}$-3 structure, yet its structural parameters deviate markedly from the established ionic-radius trend in the $A{\mathrm{Cu}}_3{\mathrm{V}}_4{\mathrm{O}}_{12}$ ($A=\mathrm{Mn}$, Cu, Ca) series. This deviation reveals local structural modifications driven by the ${\mathrm{Pb}}^{2+}$ lone-pair electrons. The compound exhibits metallic behavior down to at least 8 K and shows a moderately enhanced Sommerfeld coefficient, with density-functional calculations confirming the associated mass enhancement. Comparison of the experimental and theoretical magnetic susceptibilities further indicates an additional contribution from the Stoner mechanism. These results identify $\mathrm{PbC}{\mathrm{u}}_3{\mathrm{V}}_4{\mathrm{O}}_{12}$ as a rare example of a $3d$-electron metallic vanadate with moderate electronic correlations, demonstrating how $A$-site chemistry and lone-pair-induced local distortions can be used to engineer correlated electronic states in perovskite-related materials.

The investigation of vacancy diffusivity in metallic materials is crucial for advancing predictive models of radiation damage under extreme environmental conditions. In this work, positron annihilation spectroscopy was employed to systematically investigate the formation and diffusion mechanisms of irradiation-induced vacancies in cobalt-free NiFeMnCrAl high-entropy alloys (HEAs) and Ni subjected to 6 MeV proton irradiation. A broad activation energy spectrum for monovacancy migration, from 1.55 to 1.90 eV, is found owing to the lattice distortions and chemical complexity in HEAs. Vacancy clustering, which occurs in pure metals during thermal treatment, is suppressed in the HEAs. A complex energy landscape stems from the chemical diversity, and inherent lattice distortion leads to instability of vacancy clusters, slowing down long-distance defect diffusion – sluggish diffusion – thereby suppressing the formation of large vacancy clusters. This mechanism underpins the pronounced void swelling resistance under irradiation in multiple-component alloy systems.

The strongly correlated oxides with a honeycomb lattice have attracted vast attention due to their interesting magnetic behaviors and emergent quantum effects such as Majorana fermions generated from Kitaev spin liquid. High-quality single crystal samples with delicately controlled composition and strain are highly required in this area. In this work, honeycomb structure built by edge-sharing ${\mathrm{CoO}}_6$ octahedra is stabilized in ilmenite matrix by doping 4% Co into ${\mathrm{NaSbO}}_3$. By performing magnetic measurements and first principles calculations, it is suggested that honeycomb local motifs containing ${\mathrm{Co}}^{2+}$ $\left(3d^7\right)$ cobalt may exist in Co-doped ${\mathrm{NaSbO}}_3$ thin films, and exhibit ferromagnetic-like transition at ∼88 K. Meanwhile, the interlayer dipolar interaction may lead to antiferromagnetic coupling between the nearest layers. This work reveals the possibility to embed $3d^7$ honeycomb structure into an ilmenite matrix and provides a platform for future spin liquid exploration as well as quantum information technology.