Spin-orbit torque (SOT)-induced magnetization switching can be explained by either a single-domain coherent switching scenario or a domain-wall dynamics scenario, depending on the device size. In this study, we systematically investigate the processing effect on magnetic and SOT properties across a broad range of device sizes and geometries, from 5-µm Hall bars to submicrometer-sized pillars and magnetic tunnel junctions (MTJs), with an identical W/CoFeB/MgO magnetic heterostructure. We first examine the impact of the fabrication process and device size on the measured magnetic properties, where coercivity $H_{\mathrm{c}}$ enhances while reducing the pillar size. Next, the current-driven hysteresis loop-shift measurement is utilized to characterize the dampinglike SOT efficiency ${\xi }_{\mathrm{DL}}$, which is found to be fairly size independent. In contrast, current-induced SOT switching shows that the critical switching current density $J_{\mathrm{sw}}$ increases significantly with the device size reduction, suggesting a strong correlation between $J_{\mathrm{sw}}$ and $H_{\mathrm{c}}$. Nevertheless, the current-driven loop-shift phase diagram and the domain-wall depinning model provide a relatively consistent estimation of $J_{\mathrm{sw}}$, verifying the applicability of these two methods in the studied pillar size range. Last, we compare the SOT switching results from a micrometer-sized Hall bar device and a micrometer-sized three-terminal MTJ device, where a consistent estimated dampinglike SOT efficiency can be reached. Our results give insight into the processing and size effects on magnetic devices and provide proper protocols for SOT efficiency and critical switching current density estimations.

The anisotropic Rashba effect allows for the manipulation of electron spins in a more precise and tunable manner since the magnitude of the Rashba splitting and orientation of the spin textures can be simply controlled by tuning the direction of the externally applied electric field. Herein, we predict the emergence of the anisotropic Rashba effect in the two-dimensional (2D) Janus $X{A}_{2}Y$ constructed from group-IV ($A=\mathrm{Si},\mathrm{Sn},\mathrm{Ge}$) and group-V ($X,Y=\mathrm{Sb},\mathrm{Bi}$) elements having trigonal prismatic structures but lacking in-plane mirror symmetry. Due to the lowering point-group symmetry of the crystal, the Rashba spin splitting is enforced to become anisotropic around certain high-symmetry points in the Brillouin zone and preserves the out-of-plane spin textures. We illustrate this behavior using density functional theory calculations supplemented with $\vec{k}·\vec{p}$ analysis on the Janus ${\mathrm{SbSi}}_2\mathrm{Bi}$ monolayer as a representative example. Specifically, we observed large and anisotropic Rashba splitting with a prominent contribution of the out-of-plane spin textures in the conduction band minimum around the $M$ point and valence band maximum around the $\mathrm{\Gamma }$ point. More importantly, the anisotropic spin splitting and out-of-plane spin polarization are sensitively affected by surface imperfections, depending on the concentration and configuration of the $X$ and $Y$ elements in the 2D Janus $X{A}_{2}Y$ surface. Our paper offers the possibility to realize the present systems for spintronics applications.

Here, we study the shock wave response of semicrystalline polymers using coarse-grained molecular dynamics simulations. The crystallinity of the systems was controlled by using block copolymer-like chains with different volume fractions of crystallizable blocks. Our results indicate that the degree of initial crystallinity affects the speed of sound and the propagation velocity of shock waves at low compression velocities. However, at high compression velocities, the initial crystalline structures melt due to the passage of the shock, and the principal shock features resemble each other, independently of the crystallinity. We also found that the presence of crystalline regions helps disperse shocks, resulting in a monotonic increase in shock width with the degree of initial crystallinity. The shock-induced melting of crystalline structures was analyzed by an Avrami function, revealing similarities with conventional thermal melting. Our simulation results highlight the importance of crystalline regions and the presence of amorphous/crystal interfaces in contributing to the dispersion and dissipation of shocks and impact fronts traveling through semicrystalline polymeric materials.

We conducted comprehensive first-principles investigations of the structural, electronic, and optical properties of hexagonal $\mathrm{Zn}X$ and $\mathrm{Cd}X$ ($X=\mathrm{S},\mathrm{Se},\mathrm{Te}$) and their van der Waals heterostructures. Our results indicate that all materials are thermally and dynamically stable, in contrast to earlier works. Electronic structure calculations with a hybrid functional revealed that the bilayers $\mathrm{Zn}X$ and $\mathrm{Cd}X$ are characterized by a direct band gap (at the $\mathrm{\Gamma }$ point), primarily lies within the visible spectrum of the sunlight (with an exception for ZnS). Moreover, we found the band edges (VBM/CBM of the bilayers) lying below/above the oxidation/reduction potentials ($E^{{\mathrm{O}}_2/{\mathrm{H}}_2\mathrm{O}}/E^{{\mathrm{H}}^{+}/{\mathrm{H}}_2}$) depending on the environment's pH. The effects of mechanical strain on the electronic properties of the bilayers have been thoroughly investigated, revealing an impressive tunability of the band gap, energy position of the band edges, and the ratio of the electron and hole effective masses. The calculated optical absorption spectra showed that the bilayers $\mathrm{Zn}X$ and $\mathrm{Cd}X$, with the exception of ZnS, absorb in the visible region. Besides that, we found exciton binding energies between 0.30 and 0.96 eV for ZnTe and CdS bilayers, confirming that the reduced screening effect in 2D systems leads to higher values of exciton binding energies. Furthermore, our results indicated that the ZnTe/CdS heterostructure exhibits a band gap within the visible sunlight spectra. The band edges are located in the bilayer ZnTe resulting in a type-I band offset. However, upon compressive strain, we verified the emergence of the type-II band alignment, as a result, the first absorption peak is redshifted and the exciton exciton wave function spreads out in both materials. Overall, our findings provide valuable insights into the potential of these materials for various technological applications in the fields of the photonics, photocatalysis, and optoelectronics.

The lattice dynamic of the filled skutterudite $\mathrm{Pr}{\mathrm{Ru}}_4{\mathrm{P}}_{12}$ has been investigated by both Raman spectroscopy and density-functional theory (DFT) calculations, through the metal to insulator transition at 63 K. A $P23$ space group, which lacks inversion symmetry, is identified for the low temperature phase. The classical room-temperature $Im\overline{3}$ structure reported in the filled skutterudite family is questioned in this compound. Our results point to the $Pm\overline{3}$ space group, which already has two distinct Pr sites in the metallic state at room temperature. The consequences of symmetry breaking, between $Pm\overline{3}$ and $P23$ on both the $f$ orbital hybridization and the crystal schemes are discussed.

The integration of both optical and electronic components on a single chip, despite several challenges, holds the promise of compatibility with complementary metal-oxide semiconductor (CMOS) technology and high scalability. Among all candidate materials, III-V semiconductors exhibit great potential for optoelectronics and quantum-optics based devices, such as light emitters and harvesters. The control over geometry, and dimensionality of the III-V nanostructures, enables one to modify the band structures, and hence provide a powerful tool for tailoring the optoelectronic properties of III-V compounds. One of the most creditable approaches towards such growth control is the combination of using a patterned wafer and the self-assembled epitaxy. This work presents monolithically integrated catalyst-free InP nanowires grown selectively on Si nanotip-patterned, CMOS compatible (001) Si substrates using gas-source molecular-beam epitaxy. We use nanoheteroepitaxy approach to selectively grow InP nanowires on Si nanotips, which holds benefits due to its peculiar substrate design. In addition, our methodology allows the switching of dimensionality of the InP structures between one-dimensional nanowires and three-dimensional bulklike InP nanoislands by thermally modifying the shape of silicon nanotips surrounded by the silicon dioxide layer during the thermal cleaning of the substrate. The structural and optical characterization of nanowires indicates the coexistence of both zincblende and wurtzite InP crystal phases in nanowires. The two different crystal structures were aligned with a type-II band alignment. The luminescence from InP nanowires was measured up to 300 K, which reveals their promising optical quality for integrated photonics and optoelectronic applications.

How charge-density wave (CDW) is influenced by the change in the dimensionality is a fundamental question in condensed-matter physics. Monolayer titanium ditelluride (${\mathrm{TiTe}}_2$) undergoes $2\times 2$ CDW despite the absence of CDW in the bulk counterpart, whereas the mechanism of CDW is under intensive debate. Here we show that the CDW of monolayer ${\mathrm{TiTe}}_2$ can be conveniently switched by carrier tuning via controlling the Te ratio during molecular-beam epitaxy or depositing potassium (K) atoms on the surface. This is demonstrated by monitoring the CDW-induced $2\times 2$ band folding using angle-resolved photoemission spectroscopy. Remarkably, the CDW appears only when the inner hole pocket at the $\Gamma$ point and the elongated electron pocket at the $M$ point show partial Fermi-surface nesting. The present study suggests that the carrier doping is an effective method to pin down the mechanism of CDW in atomic-layer transition-metal dichalcogenides.

In this contribution, we extend the current understanding of energy-trapping mechanisms in wide-band-gap inorganic crystals via the formation and decay of the self-trapped exciton (STE) using pure and copper-doped lithium fluoride (LiF) nanoparticles. The study aims at filling in some of the knowledge gaps underpinning the search for enhanced dosimetric performance, enabling novel 3D imaging techniques based on transparent materials exhibiting intrinsic scintillation phenomena. Here, LiF stands out as the lightest and highest-band-gap dielectric. We use a combination of luminescence-spectroscopy techniques at low and elevated temperatures to confirm the role of an STE triplet state as the radiative recombination center driving ionizing-radiation-induced luminescence phenomena centered at 325 nm, namely radioluminescence and optically stimulated luminescence (OSL). We demonstrate that the role of copper doping as a luminescence enhancer is based on the trapping of the self-trapped hole at room temperature, which would otherwise become mobile allowing for hopping of electronic excitation in the lattice at temperatures above 150 K. Finally, we show results from optimization studies aiming at establishing the best synthesis parameters in terms of OSL yield and discuss in more detail the role of the nanoparticle surface, possible energy trapping, and recombination pathways.

The dislocation core structure has a significant role in determining the dominant slip plane and the magnitude of the Peierls stress for a dislocation. An important challenge when studying dislocation cores is to determine the stable and metastable core morphologies, and then relate these structures to the dynamics of the dislocations. This study introduces a method for identifying core structures that are metastable at zero temperature. Application of this method to $\langle a\rangle$-type screw dislocations in $\alpha$-Ti (as described using an empirical potential) reveals a multitude of (meta)stable nonplanar cores. Molecular dynamics studies show how the competing metastable core structures determine the properties of the dislocations at temperature and under a range of non-Schmid stresses.

Climate change motivates the search for non-carbon-emitting energy generation and storage solutions. Metal hydrides show promising characteristics for this purpose. They can be further stabilized by tailoring the negative pressure of microstructural and structural defects. Using systematic ab initio and atomistic simulations, we demonstrate that an enhancement in the formation of hydrides at the negatively pressurized tip region of the microcrack is feasible by increasing the mechanical tensile load on the specimen. The theoretical predictions have been used to reassess and interpret atom probe tomography experiments for a high-strength 7XXX-aluminium alloy that show a substantial enhancement of hydrogen concentration at structural defects near a stress-corrosion crack tip. These results contain important implications for enhancing the capability of metals as H-storage materials.

${\mathrm{PrRhC}}_2$ belongs to the rare-earth carbides family, whose properties are of special interest among topological semimetals due to the simultaneous breaking of both inversion and time-reversal symmetry. The concomitant absence of both symmetries grants the possibility to tune the Weyl nodes chirality and to enhance topological effects such as the chiral anomaly. In this paper, we report on the synthesis and compare the magnetotransport measurements of polycrystalline ${\mathrm{PrRhC}}_2$ samples and a single-crystalline ${\mathrm{PrRhC}}_2$ sample. Using a remarkable and sophisticated technique, the ${\mathrm{PrRhC}}_2$ single crystal is prepared via focused-ion-beam cutting from the polycrystalline material. Our magnetometric and specific heat analyses reveal a noncollinear antiferromagnetic state below $20\mathrm{K}$, as well as short-range magnetic correlations and/or magnetic fluctuations well above the onset of the magnetic transition. The transport measurements on the ${\mathrm{PrRhC}}_2$ single crystal display an electrical resistivity peak at $3\mathrm{K}$ and an anomalous Hall effect below $6\mathrm{K}$ indicative of a net magnetization component in the ordered state. Furthermore, we study the angular variation of magnetoresistivities as a function of the angle between the in-plane magnetic field and the injected electrical current. We find that both the transverse and the longitudinal resistivities exhibit fourfold angular dependencies due to higher-order terms in the resistivity tensor, consistent with the orthorhombic crystal symmetry of ${\mathrm{PrRhC}}_2$. Our experimental results may be interpreted as features of topological Weyl semimetallic behavior in the magnetotransport properties.

We successfully synthesized $\left(p\text{−}\mathrm{Py}\text{−}\mathrm{V}\right)\left[{\mathrm{Cu}\left(\mathrm{hfac}\right)}_2\right]$, a verdazyl-based complex. Molecular orbital calculations revealed five types of intermolecular interactions between the radical spins and two types of intramolecular interactions between the radical and the Cu spins, resulting in a spin-1/2 distorted honeycomb-based lattice. Additionally, competing ferromagnetic and antiferromagnetic (AF) interactions induce frustration. The magnetization curve displayed a multistage increase, including a zero-field energy gap. Considering the stronger AF interactions that form dimers and tetramers, the magnetic susceptibility and magnetization curves were qualitatively explained. These findings demonstrated that the quantum state, based on the dominant AF interactions, was stabilized due to the effects of frustration in the lattice. Hence, the exchange interactions forming two-dimensional couplings decoupled, reducing energy loss caused by frustration and leading to frustration-induced dimensional reduction.

We investigate the crystallographic and magnetic properties of a chromium-based thiospinel ${\mathrm{CuGaCr}}_4{\mathrm{S}}_8$. From a synchrotron x-ray diffraction experiment and structural refinement, Cu and Ga atoms are found to occupy the tetrahedral A sites in an alternate way, yielding breathing pyrochlore Cr network. ${\mathrm{CuGaCr}}_4{\mathrm{S}}_8$ undergoes a magnetic transition associated with a structural distortion at 31 K in zero magnetic field, indicating that the spin-lattice coupling is responsible for relieving the geometrical frustration. When applying a pulsed high magnetic field, a sharp metamagnetic transition takes place at 40 T, followed by a 1/2-magnetization plateau up to 103 T. These phase transitions accompany dielectric anomalies, suggesting the presence of helical spin correlations in low-field phases. The density functional theory calculations suggest that ${\mathrm{CuGaCr}}_4{\mathrm{S}}_8$ is dominated by antiferromagnetic and ferromagnetic exchange couplings within small and large tetrahedra, respectively, in analogy with ${\mathrm{CuInCr}}_4{\mathrm{S}}_8$. We argue that A-site-ordered Cr thiospinels serve as an excellent platform to explore diverse magnetic phases along with pronounced magnetoelastic and magnetodielectric responses.

Exploring the uncharacterized magnetic phases of ${\mathrm{Co}}^{2+}$ chain compounds is critical for finding new low-dimensional magnets hosting quantized excitations. We map the unexplored magnetic phases of the ${\mathrm{Co}}^{2+}$ chain compound ${\mathrm{Li}}_2{\mathrm{CoCl}}_4$. Magnetometry reveals magnetic ordering below 7 K with a metamagnetic transition near 16.5 kOe and a gradual transition to a field-aligned paramagnetic state above 31 kOe. Curie-Weiss fits to the high-temperature susceptibility reveal a high-spin (spin-$\frac{3}{2}$) state for cobalt. Heat capacity data, though, give a magnetic entropy change of 5.46 J/mol, consistent with cobalt effective spin-$\frac{1}{2}$ systems. To characterize the zero-field antiferromagnetic ordering, we separately calculated the energy of proposed magnetic structures with density functional theory and collected 3.5 K neutron diffraction data, finding that ${\mathrm{Li}}_2{\mathrm{CoCl}}_4$ has ferromagnetic chains with antiferromagnetic interactions between them. Increasing field rotates these spin chains, producing the antiferromagnetic to intermediate to paramagnetic transition sequence.

Dual-phase $\gamma$-TiAl and ${\alpha }_2\text{−}{\mathrm{Ti}}_3\mathrm{Al}$ alloys exhibit high strength and creep resistance at high temperatures. However, they suffer from low tensile ductility and fracture toughness at room temperature. Experimental studies show unusual plastic behavior associated with ordinary and superdislocations, making it necessary to gain a detailed understanding on their core properties in individual phases and at the two-phase interfaces. Unfortunately, extended superdislocation cores are widely dissociated beyond the length scales practical for routine first-principles density-functional theory (DFT) calculations, while extant interatomic potentials are not quantitatively accurate to reveal mechanistic origins of the unusual core-related behavior in either phases. Here, we develop a highly accurate moment tensor potential (MTP) for the binary Ti-Al alloy system using a DFT dataset covering a broad range of intermetallic and solid solution structures. The optimized MTP is rigorously benchmarked against both previous and new DFT calculations, and unlike existing potentials, is shown to possess outstanding accuracy in nearly all tested mechanical properties, including lattice parameters, elastic constants, surface energies, and generalized stacking fault energies (GSFE) in both phases. The utility of the MTP is further demonstrated by producing dislocation core structures largely consistent with expectations from DFT-GSFE and experimental observations. The new MTP opens the path to realistic modeling and simulations of bulk lattice and defect properties relevant to the plastic deformation and fracture processes in $\gamma$-TiAl and ${\alpha }_2\text{−}{\mathrm{Ti}}_3\mathrm{Al}$ dual-phase alloys.

A quantitative understanding of the electron-phonon interaction is important, particularly for the thermal management of electronic devices, which are built mostly on doped silicon. Here, we performed inelastic x-ray scattering measurements on electron-doped and hole-doped bulk silicon crystals along $\mathrm{\Gamma }\text{−}X$ and directly quantified the mode- and momentum-dependent electron-phonon scattering rates of the optical phonon modes. We found the electron-phonon interaction as has been indicated; in electron-doped silicon, phonon scattering by this interaction occurs around 0.3 $\mathrm{\Gamma }\text{−}X$ for the longitudinal phonon mode, supporting the $g$-type intervalley scattering. In hole-doped silicon, a nonzero scattering rate is observed only in the vicinity of the zone center. The experimental results quantitatively agree with the calculations, which also explain the experimental results of the thermal conductivity.