Eu-based Zintl materials have recently received considerable attention due to their unique properties and application potentials. Herein, we grew $\mathrm{EuA}{\mathrm{l}}_2\mathrm{S}{\mathrm{i}}_2$ single crystals and studied the magnetic susceptibility, magnetoresistance, angular magnetoresistance, and band structures. Magnetic susceptibility and magnetization data establish $\mathrm{EuA}{\mathrm{l}}_2\mathrm{S}{\mathrm{i}}_2$ as an antiferromagnet with short-range ferromagnetic correlations. Its resistivity shows metallic behavior, and well-defined peaks around the Néel temperature, indicative of the presence of magnetic fluctuations. Under magnetic field, the resistivity peak decreases, while the low-temperature resistivity increases, demonstrating respective negative and positive magnetoresistance. An analysis using the Kohler rule and Bethe-ansatz theory reveals that the low- and high-temperature magnetoresistance may result from moderate carrier compensation, and suppressed magnetic fluctuations or reduced hopping energy owing to the increased size of magnetic polarons, respectively. Furthermore, the angular magnetoresistance measurements uncover $\mathrm{EuA}{\mathrm{l}}_2\mathrm{S}{\mathrm{i}}_2$'s moderate electronic anisotropy. Our theoretical studies not only corroborate these results, but also reveal topologically nontrivial band structures that evolve across magnetic phase transitions. These findings demonstrate the crucial role of magnetic orders in determining transport and electronic properties of $\mathrm{EuA}{\mathrm{l}}_2\mathrm{S}{\mathrm{i}}_2$, while establishing the Zintl phase as a promising material platform for exploring emergent quantum phenomena arising from the interplay of magnetism, transport, and topology.

Disordered solids, straddling the solid-fluid boundary, lack a comprehensive continuum mechanical description. They exhibit a complex microstructure wherein multiple metastable states exist. Deforming disordered solids induces particle rearrangements enabling the system to transition between metastable states. A dramatic consequence of these transitions is that quasistatic deformation cycles modify the reference state, facilitating the storage and release of mechanical energy. Here we develop a continuum mechanical theory of disordered solids, which accounts for the absence of a reference state and the lack of conserved potential energy. Our theory, which introduces a new modulus describing nonconservative mechanical screening, reduces to classical elasticity in the absence of screening. We analytically derive predictions for the deformation field for various perturbations and geometries, and predict anomalous mechanical response that break chiral symmetry. While our theory applies to general disordered solids, we focus on a two-dimensional disordered granular system and predict accurately the nonaffine displacement fields observed in experiments for both small and large deformations, along with the observable vanishing shear modulus. The proposed moduli satisfy universal relations that are independent of the specific experimental realization. Our work thus forms the basis of an entirely new family of continuum descriptions of the mechanics of disordered solids.

A detailed study of the field-induced entropy change evolution under hydrostatic pressure ($p$) of the well-known skyrmion-hosting MnSi system was carried with the goal of assessing its magnetocaloric properties and identifying the skyrmion phase. The pressure-induced modification of the first-order phase transition boundary of the skyrmion phase in MnSi has been determined through the field-exponent, $n\left(T,B\right)$, of the isothermal entropy change $\left[\mathrm{\Delta }S\alpha {\left(B\right)}^n\right]$. The skyrmion phase boundaries generated from $n\left(T,B\right)$ and ac-susceptibility data are in qualitatively good agreement at ambient pressure. The application of hydrostatic pressure can lower the transition temperature of MnSi towards the hydrogen liquefaction temperature (∼20 K) while retaining the first-order nature of the phase transition up to the highest applied pressure of $p=9.8\mathrm{kbar}$. As a result, the studied system maintains good magnetocaloric properties near 20 K $\left[\right|\mathrm{\Delta }S|=4.24\mathrm{J}/\mathrm{kg}\mathrm{K}$, adiabatic temperature change $|\mathrm{\Delta }{T}_{\mathrm{ad}}|=4.62\mathrm{K}$ (estimated), and refrigerant capacity $\left|RC\right|=91.37\mathrm{J}/\mathrm{kg}$ for $\mathrm{\Delta }B=7\mathrm{T}$ with $p=9.8\mathrm{kbar}]$, which are comparable to those of light rare-earth Laves phase compounds with the added benefit of being composed of cheap and abundant elements.

We carried out a comprehensive crystal structure characterization of ${\mathrm{Li}}_2{\mathrm{Ti}}_x{\mathrm{Ru}}_{1-x}{\mathrm{O}}_3$ to investigate the effect of Ti-doping on the structural phase transition arising from the melting of the dimer solid around 550 K. Experimental tools sensitive to the average structure (x-ray diffraction), as well as those sensitive to local structure (extended x-ray absorption fine structure, EXAFS; pair distribution function, PDF) are used. We observed nonmonotonic dependence of the structural transition temperature on the Ti-doping level. At low doping, the transition temperature slightly increases with doping, while at high doping, the temperature decreases significantly with doping. We note two important observations from our studies. First, Ti K-edge EXAFS data show persistent Ti-Ru dimerization even with substantial Ti doping. Second, we were able to use the PDF data to estimate the correlation length above the transition temperature, which would correspond to the size of the proposed local ‘dimer clusters’ formed by Ru-Ru and Ti-Ru neighbors. The correlation length is found to be around 10 Å, which remains robust regardless of doping. Our study therefore suggests that ${\mathrm{Ti}}^{4+}$ with its $d^0$ electronic configuration is a special type of dopant when replacing Ru.

We employ first-principles calculations to investigate the ferroelectric properties and the bulk photovoltaic effect (BPVE) of antimony sulfur iodide (SbSI). The BPVE enables direct sunlight-to-electricity conversion in homogeneous materials and, in ferroelectric compounds, can be tuned via an electric field controlling the polarization. However, most ferroelectrics are oxides with large band gaps exceeding the energy of visible light, thereby limiting their photovoltaic performance. SbSI, featuring a visible-range band gap, combines remarkable photovoltaic capabilities with a spin-textured band structure, coupling charge and spin degrees of freedom. Our calculations predict ferroelectric and antiferroelectric phases with comparable band gaps but distinct spin textures, relevant for spintronics applications. The BPVE is driven by the linear and circular photogalvanic effects, exhibiting high photoconductivities under visible light. Furthermore, it serves as a diagnostic tool to identify the material phase, with the circular photogalvanic effect reflecting spin texture changes. Thanks to its multifunctional properties, SbSI emerges as a promising candidate for solar energy conversion and advanced electronics, with potential applications extending to spintronics.

Low-dimensional topological states have transformed our understanding of charge transportation through quantum materials. Many relevant observations have been connected to bismuth (Bi) containing materials or ultrathin Bi films. Here, we studied sub-monolayer amounts of Bi deposition on the In-terminated InSb(111)A surface using various complementary surface science techniques. Bi deposition at elevated sample temperature results in well-ordered $(2\times 2)$ and $(2\surd 3\times 2\surd 3)\text{−}\mathrm{R}{30}^{\circ }$ surface reconstructions. Scanning tunneling microscopy/spectroscopy (STM/S) data show an enhanced density of states at the interface of the two reconstructions and local Bi trimers over the $(2\times 2)$ reconstructed surface. Bi-induced metallic surface states crossing the Fermi level are observed and attributed exclusively to the localized trimer states through STS and angle-resolved photoemission spectroscopy (ARPES) results. Furthermore, the ARPES spectra show band splitting at the Γ point and degenerate surface states at the M point, which is associated with Rashba splitting due to strong Bi-substrate interaction. Thus we interpret the Bi/InSb(111)A, exhibiting spin-split metallic surface states induced by localized Bi structures, as a promising candidate for exploring low-dimensional states and spin dynamics in future quantum materials.

Achieving frequency tunability by utilizing material properties rather than altering geometric structures is highly attractive due to its lightness and processability. $\mathrm{B}{\mathrm{a}}_x\mathrm{S}{\mathrm{r}}_{1-x}\mathrm{Ti}{\mathrm{O}}_3$ (BSTO) has been a widely used ferroelectric in tunable microwave devices due to its large dielectric constants, high electric field tunability, and low microwave losses. However, due to the narrow temperature range of the high tunability for conventional single-composition ferroelectric material, which can only be achieved in the vicinity of the Curie temperature ($T_{\mathrm{C}}$), this results in difficulty for the resulting devices to work stably in harsh operating environments. To overcome this challenge, thin films with gradient composition have emerged as a promising strategy to achieve improved dielectric tunability across a wide temperature range. In this study, we employed an advanced combinatorial synthesis technique to fabricate composition-spread BSTO films from $\mathrm{SrTi}{\mathrm{O}}_3$ to $\mathrm{BaTi}{\mathrm{O}}_3$ (i.e., $0\le x\le 1$) on a single piece of ${\left(\mathrm{LaAl}{\mathrm{O}}_3\right)}_{0.3}{\left(\mathrm{S}{\mathrm{r}}_2\mathrm{TaAl}{\mathrm{O}}_6\right)}_{0.7}$ substrate. By characterizing the complex impedances of interdigital capacitors (IDCs) with 270-µm width fabricated at different compositions of the film, we extract the doping dependencies of tunability and ferroelectric transition temperature, which qualitatively agree with the results from single-composition films. A comparison between short IDCs (nearly single-component) and composition-span IDCs demonstrated improvement in the temperature stability of composition-spread BSTO film. These findings prove the effectiveness of the combinatorial technique for optimizing the dielectric properties of ferroelectric materials.

Rutile ${\mathrm{GeO}}_2$ is an emerging ultra-wide band gap semiconductor (UWBG) that has demonstrated excellent potential for applications in power electronic devices. Alloys of rutile ${\mathrm{SnO}}_2$, a well-established UWBG semiconducting oxide, with ${\mathrm{GeO}}_2$ are promising for tuning the material properties for applications. The thermal conductivity, in particular, is a key property, which is significantly impacted by alloy disorder, but which is also essential in assessing the operation and degradation of materials in high-power electronic applications. Here, we present first-principles calculations of the thermal conductivity of rutile ${\mathrm{GeO}}_2, {\mathrm{SnO}}_2$, and their alloys, and quantify the effects of scattering by alloy disorder, temperature, and isotope mass distribution. We show that the relatively high thermal conductivity of the binary compounds is reduced by alloying and isotope disorder. We further assess grain boundary effects via quantifying the impact of phonon mean free path. However, we also find that the room-temperature thermal conductivity of the alloys is still comparable to or surpasses the values for $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$, an established UWBG semiconducting oxide. Our findings provide a roadmap for the co-design of the thermal properties of rutile ${\mathrm{Ge}}_x{\mathrm{Sn}}_{1-x}{\mathrm{O}}_2$ alloys for electronic device applications.

Magnetic field-tunable transport phenomena, especially giant magnetoresistance in quantum materials, remain critical for unlocking fundamental physics and next-generation spintronic devices. Here, we synthesized a series of $\mathrm{ZrT}{\mathrm{e}}_5$ single crystals with different Te deficiencies through precisely controlling growth conditions. By systematically tuning Te-vacancy concentrations in $\mathrm{ZrT}{\mathrm{e}}_5$ crystals, we observe a progressive suppression of the resistivity cusp from 135 to 2 K, where the near-stoichiometric one exhibits semiconducting behavior. Magnetoresistance of the as-synthesized ${\mathrm{ZrTe}}_5$ single crystals can also be manipulated, reaching a maximum of $1.12\times {10}^4\%$ at 2 K and 9 T. A Two-band model analysis of magnetoresistance and Hall resistance reveals that the unique transport evolution originates from defect-induced variations in Fermi level, which affect the carrier concentration and mobility within $\mathrm{ZrT}{\mathrm{e}}_5$ crystals. Our work proposes that engineered defects may open up an avenue to tailor the physical properties of $\mathrm{ZrT}{\mathrm{e}}_5$ and related materials and explore different device functionalities.

We report a large near-infrared (NIR) optical diode effect (ODE) and its electric field switching in the antiferromagnetic state of ${\mathrm{LiFePO}}_4$. The difference in absorption coefficients for light travelling in opposite directions, divided by the sum, reaches $\sim 25\%$ at a photon energy of 1.18 eV. Symmetry analysis attributes the ODE to the spin-allowed $d\text{−}d$ transitions of octahedrally coordinated $\mathrm{F}{\mathrm{e}}^{2+}$ via the spin-orbit interaction. Given the abundance of iron and potentially high magnetic transition temperature in iron-based materials, this study may open the door to the application of the NIR ODE.

In this study, we investigate the electronic, magnetic properties of $\text{SnC/MnSe}X$ ($X=\text{Se},\text{Te}$) heterostructures using density functional theory (DFT) and atomistic spin simulations. The $\mathrm{SnC}/{\mathrm{MnSe}}_2$ heterostructure exhibits half-metallicity, while SnC/MnSeTe and SnC/MnTeSe display metallic behavior. Noncollinear calculations reveal an out-of-plane easy magnetization axis for $\mathrm{SnC}/{\mathrm{MnSe}}_2$ and SnC/MnTeSe, while SnC/MnSeTe has an in-plane axis. The Curie temperature ($T_{\mathrm{c}}$) is significantly enhanced in $\mathrm{SnC}/{\mathrm{MnSe}}_2$, demonstrating the potential for robust magnetic ordering. Moreover, we highlight the crucial role of the Dzyaloshinskii-Moriya interaction (DMI) in stabilizing skyrmions, emphasizing its enhancement through inversion symmetry breaking. Notably, the resulting DMI values are comparable to those in well-known skyrmion-hosting materials such as Co/Pt and Fe/Ir. Néel-type skyrmions form in these heterostructures, exhibiting tunable stability under varying temperature, magnetic fields, and electric fields. This tunability allows control over skyrmion size, phase transitions, and energy barriers, highlighting the promise of $\text{SnC/MnSe}X$ for next-generation spintronic applications such as high-density data storage and advanced computing technologies.

In orthorhombic perovskite oxides (${RM\mathrm{O}}_3$), substituting $R^{3+}$ rare-earth cations tailors the spin, orbital, and charge degrees of freedom of the central $M^{3+}$ transition metal cations through lattice distortions. In turn, these modify also the surrounding environment of $R^{3+}$. When both $R^{3+}$ and $M^{3+}$ exhibit magnetic properties, phenomena such as spin reorientation and magnetization reversal can occur. In fact, the underlying exchange interactions between $M\text{−}3d$ spins and $R\text{−}4f$ magnetic moments enrich the multifunctional character of ${RM\mathrm{O}}_3$, particularly when combined with structural distortions. They play a crucial role in achieving appealing properties such as robust magnetoelectricity with noncollinear magnetic orders. Here, we explore the exchange coupling in epitaxial ${\mathrm{PrVO}}_3$ thin films, selectively probing the magnetism of cation sublattices, and uncovering simultaneous ${\mathrm{V}}^{3+}3d$ spin reorientation and ${\mathrm{Pr}}^{3+}4f$ magnetization reversal using spectroscopy techniques. By strain engineering, we manipulate the lattice distortions to rationalize their role in coupling $3d$ spins and $4f$ magnetic moments. Theorectical calculations show that octahedral rotations and Jahn-Teller distortions act as tuning mechanisms, promoting competition between orbital and spin orders. The observed coupling between magnetic cations and lattice distortions can be extended to other orthorhombic ${RM\mathrm{O}}_3$ systems, advancing the understanding of controlling spins in engineered perovskite heterostructures and superlattices.

We report the presence of a magnetic compensation (MC) composition at room temperature in 20 nm thick ${\mathrm{Mn}}_{4-x}{\mathrm{Ag}}_x\mathrm{N}$ $(x=0-1.0)$ epitaxial thin films prepared on ${\mathrm{SrTiO}}_3\left(001\right)$ by molecular beam epitaxy and show that their magnetic structure is significantly altered by Ag doping. Magnetization curves and anomalous Hall effect loops indicate the presence of an MC composition $x_{\mathrm{MC}}\sim 0$.15 at room temperature. X-ray absorption near-edge structure measurements reveal preferential substitution of Ag for Mn atoms at the corner sites. X-ray magnetic circular dichroism measurements show that the magnetic structure changes drastically for $x>x_{\mathrm{MC}}$. These results and various considerations suggest that the ${\mathrm{Mn}}_{4-x}{\mathrm{Ag}}_x\mathrm{N}$ thin film constitutes a noncollinear magnetic structure above $x_{\mathrm{MC}}$. This is significantly different from the previously reported Ni- and Co-doped ${\mathrm{Mn}}_4\mathrm{N}$ epitaxial thin films.

Solid solution strengthening (SSS) significantly influences the mechanical properties of alloy materials, which strongly depends on the solute type and concentration and various alloy structures. However, it still presents a significant challenge to identify a universal structure-property relationship of SSS. Here, we propose an intrinsic descriptor to quantify the electronic effect of SSS for both dilute and concentrated alloys from the point of bond breaking and forming, which allows to evaluate the SSS effect across various alloys, such as binary, medium-entropy, and high-entropy alloys, regardless of the solute type and concentration and alloy structures. Our descriptor reflects the key parameter—solute/dislocation interactions, indicates that the center and upper edge of d-bands control the SSS effects, and identifies that the d-d/d-s coupling dominates the size effects of SSS for dilute alloys and the d-d coupling for concentrated alloys. This simple element-determined recipe provides a deep understanding of the SSS mechanism and a physical guidance for designing high-performance alloys.

A tetragonally distorted FeCo alloy is a ferromagnetic material exhibiting perpendicular magnetic anisotropy (PMA) with a large saturation magnetization. Theoretical investigations have proposed that PMA in FeCo is caused by the hybridization of the certain orbitals near the Fermi energy ($E_{\mathrm{F}}$) in the minority-spin channel, but experimental verification of the electronic structure has yet to be performed. Here, using spin- and angle-resolved photoemission spectroscopy (SARPES) combined with first-principles calculations, we investigated the spin- and orbital-dependent electronic structure of tetragonally distorted FeCo films on a Rh(001) substrate. Our SARPES results show clear out-of-plane spin polarization at room temperature. Furthermore, by considering the matrix element effect and experimental geometry, we revealed that the spin-polarized bands around $E_{\mathrm{F}}$ of FeCo films possessing PMA are mainly composed of minority-spin $d_{xy}$ and $d_{x^2-y^2}$ orbitals. Our findings provide deep insight into the emergence of PMA in rare-element-free magnetic materials.

Amorphous alumina thin films (TFs) have attracted great attention in the last decade due to their unconventional properties that are distinct from other oxide glasses. The ion migration mechanism was systematically investigated for surface amorphous alumina TFs on aluminum in comparison with bulk amorphous/crystalline alumina by using reactive molecular dynamics simulations combined with free-energy calculations. The results reveal that the ion migration mechanism within the surface alumina TFs on Al is different from that of bulk alumina due to the incorporation of Al at the interface. We show that incorporating Al into surface alumina TF remarkably decreases the ion migration barriers to around 1 eV by increasing the ion site volume along the migration paths. The calculated ion diffusivity in surface alumina above the Al melting point significantly increases to ${10}^{-8}\sim {10}^{-6}\mathrm{c}{\mathrm{m}}^2/\mathrm{s}$, lowering the temperature threshold for massive ion migration by $\sim 1000$ K. We finally discussed the temperature and structural anisotropy dependence for activating the ion migration in the surface oxide TF. The results reveal the atomistic origin of the enhanced ion migration within surface alumina TF and provide insights into thermal oxidation mechanism of metal/alloy-based energetic materials.