Strong Pinning Research Articles

Highly Selective, Room-Temperature Triethylamine Sensor Using Humidity-Resistant Novel TiZn Alloy Nanoparticles-Decorated MoS₂ Nanosheets.

The future of environmental monitoring, medical diagnostics, and industrial safety depends on developing room-temperature, long-term operable, stable, miniaturized, ultrahigh-performance sensors integrated into the Internet of Things (IoT). While noble metals and high-entropy alloys (HEAs) lead in addressing the limitations of conventional transition-metal dichalcogenides (TMDs) like MoS₂, they face challenges such as high-cost, limited availability, and fabrication complexity. To address this, multifunctional, cost-effective, humidity-insensitive novel phase Ti₀.₅Zn₀.₅ (TiZn) alloy nanoparticle-decorated MoS₂ nanosheets (MoS₂_NP) is developed for ultra-selective and highly sensitive triethylamine (TEA) vapor detection at room temperature (RT). This exhibited a 24-fold increase in response compared to MoS₂, with a high signal-to-noise ratio, negligible humidity interference, sensitivity of 9.92×10⁻⁵ ppm⁻¹ at RT, and a detection limit of 48ppm. The enhanced catalytic activity and defect concentration, the reduction of the edge oxidation resulting in strong Fermi-level pinning, and the relatively high adsorption energy lead to a target gas-specific carrier-type response, demonstrating the potential of binary alloy nanoparticles (NPs) as decorative materials for enhanced sensing applications. The superior performance of the sensor led to the development of a TEA detection prototype interfaced with a mobile device via IoT for continuous monitoring, enhancing practicality and usability by offering immediate access to critical information.

Quasi-Zero-Dimensional Source/Drain Contact for Fermi-Level Unpinning in a Tungsten Diselenide (WSe2) Transistor: Approaching Schottky-Mott Limit.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) known for their exceptional electrical and optical properties have emerged as promising channel materials for next-generation electronics. However, as strong Fermi-level pinning (FLP) between the metal and the 2D TMDC material at the source/drain (S/D) contact decides the Schottky barrier height (SBH), the transistor polarity is fixed to a certain type, which remains a challenge for the 2D TMDC field-effect transistors (FETs). Here, a S/D contact structure with a quasi-zero-dimensional (quasi-0D) contact interface, in which the dimensionality reduction effect alleviates FLP, was developed to gain controllability over the polarity of the 2D TMDC FET. As a result, conventional metal contacts on the WSe2 FET showed n-type characteristics due to strong FLP (pinning factor of 0.06) near the conduction band, and the proposed quasi-0D contact enabled by the Ag conductive filament on the WSe2 FET exhibited p-type characteristics with a SBH very close to the Schottky-Mott rule (pinning factor of 0.95). Furthermore, modeling of Schottky barriers of conventional contacts, one-dimensional (1D) contacts, and quasi-0D contacts revealed that the SBH of the quasi-0D contact is relatively less subject to interface dipoles that induce FLP, owing to more rapid decaying of dipole energy. The proposed contact in this study provided a method that progressed beyond the alleviation of FLP to achieve controllable polarity. Moreover, reducing the contact dimensionality to quasi-0D will enable high compatibility with the further scaled-down nanoscale device contact structure.

Depinning of charge density waves of different dimensionalities in 1T-TiSe2 and NbSe3

Nonlinear transport behavior is one of the signatures of the formation of electronic crystals such as charge density wave (CDW), as it provides evidence for their collective motion. Such experimental evidence has been widely reported in quasi-one-dimensional (1D) materials but is rarely studied in 2D systems. Only a few studies on the RTe3materials have been previsouly reported. Here we report for the first time the observation of CDW depinning and sliding in the layered 1T-TiSe2compound, based on the observation of (1) nonlinear voltage-current characteristics and (2) the electrical noise, which are associated with the CDW depinning and sliding process. Similar measurements are also conducted on quasi-1D system NbSe3. The depinning behavior of the CDWs with different dimensionalities in these two systems are compared. It is found that the threshold electric field (ET) increases linearly with decreasing temperature for the 2D case, consistent with previous results on RTe3, while it demonstrated an activated behavior in 1D, as expected within the weak-pinning Fukuyama-Lee-Rice framework. Such a distinction of the threshold behavior in CDW systems of different dimensions therefore indicates a possible strong pinning picture in higher-dimensional CDW systems in general.ETis found to be much higher in 1T-TiSe2, consistent with a strong pinning picture, and could account for the scarcity of the depinning study in these 2D systems. Our results thus pave the way for a unified understanding of the CDW collective motion in different dimensionalities.

Origins of strength stabilities at elevated temperatures in additively manufactured refractory high entropy alloy

While refractory high-entropy alloys (RHEAs) show promising potential for extreme applications, those directly fabricated via additive manufacturing methods have been hindered by their inferior mechanical properties, particularly at high temperatures. In this study, we successfully produced a Hf-Nb-Ti-V RHEA using directed energy deposition (DED) technique, achieving satisfactory tensile properties across a wide temperature range. This was accomplished by inducing severe lattice distortions in the fabricated RHEA, which can be traced back to the local chemical fluctuations present in the newly fabricated RHEA and the significant atomic radius mismatch. Due to strong solute pinning, these factors contribute to the superior yield strength of the DED-fabricated RHEA across a wide temperature range. Furthermore, the elastic constants in the fabricated RHEA show a negligible temperature dependence, revealed by first-principles calculations, ensuring satisfactory strengths even at high temperatures. This alloy design strategy, which involves introducing significant lattice distortion and maintaining the temperature-low sensitivity of the elastic moduli, opens up new possibilities for directly fabricating RHEAs with superior high-temperature properties.

Stoichiometric and non-stoichiometric Mn modification on high-power properties in PYN-PZT piezoelectric ceramics

The types of dopants lead to distinctive microstructural evolution behavior and physical properties in materials. In this study, the effect of stoichiometric and non-stoichiometric Mn modification, namely Pb(Mn1/3Nb2/3)O3 (PMnN) and MnO2, on the microstructure and properties of Pb(Yb1/2Nb1/2)O3-PbZrO3-PbTiO3 (PYN-PZT) piezoelectric ceramics are systematically investigated. It was found that stoichiometric PMnN modification inhibits the grain growth while non-stoichiometric MnO2 modification promotes it, and thus the former yields stronger high-power characteristics (higher internal bias field Ei and larger mechanical quality factor Qm) than the latter. Specifically, with an equivalent amount of Mn modification (2 mol%), PMnN and MnO2 modification PYN-PZT ceramics exhibit significantly different values for average grain size (1.21 μm vs. 14.12 μm), Ei (8.5 kV/cm vs. 5 kV/cm), and Qm (2376 vs.1134). To further evaluate high-power performance, the vibration velocity v of these two modified PYN-PZT under high driving conditions was measured. Under an AC electric field of 3.5 V/mm, the PYN-PZT+6PMnN ceramics exhibit a v of up to 0.95 m s−1, larger than both MnO2-doped PYN-PZT (0.72 m s−1) and unmodified PYN-PZT ceramics (0.1 m s−1), and far outperformance than both PZT-4 and PZT-8 ceramics. Furthermore, to elucidate the origin of the exceptional high-power performance of PMnN-modified PYN-PZT, we performed phase-field simulations revealing a pinning effect of the grain boundary on domain wall motion. Consequently, the small grain size (high grain boundary density) in PMnN-modified PYN-PZT exhibits a strong pinning effect, resulting in a large Qm and outstanding high-power performance.

Strong pinning effect on domains in piezoelectrics

In high-power applications, since mechanical losses in piezoelectric devices always result in considerable heat generation, the temperature stability of the mechanical quality factor (Qm) is particularly crucial and should be considered in real piezoelectric applications. Here, we propose a poling-aging-repoling strategy to make the defect dipoles aligned with the poling direction as much as possible, thereby resulting in the strong pinning of ferroelectric domains. A giant internal bias field Ei (11.6 kV cm−1 @ 1 Hz) and a high Qm (2074), accompanied by almost unchanged d33, are obtained in the composition of CuO-doped (K0.48Na0.52)0.94Li0.06Nb0.94Ta0.06O3 (KNNLT-Cu) ceramics with a diffused polymorphic phase transition. Furthermore, and this is more encouraging, the high electromechanical performance exhibits good temperature stability in the range from room temperature to 100 °C, suggesting that the thermal stability of Qm can be effectively improved by combining the strong pinning of defect dipoles with composition design and providing a way for the development and design of future high-power piezoelectric devices.

Theoretical model of dynamics and stability of nanobubbles on heterogeneous surfaces

Surface nanobubbles have revealed a new mechanism of gas–liquid–solid interaction at the nanoscale; however, the nanobubble evolution on real substrates is still veiled, because the experimental observation of contact line motions at the nanoscale is too difficult. HypothesisThis study proposes a theoretical model to describe the dynamics and stability of nanobubbles on heterogeneous substrates. It simultaneously considers the diffusive equilibrium of the liquid–gas interface and the mechanical equilibrium at the contact line, and introduces a surface energy function to express the substrate’s heterogeneity. ValidationThe present model unifies the nanoscale stability and the microscale instability of surface bubbles. The theoretical predictions are highly consistent to the nanobubble morphology on heterogeneous surfaces observed in experiments. As the nanobubbles grow, a lower Laplace pressure leads to weaker gas adsorption, and the mechanical equilibrium can eventually revert to the classical Young-Laplace equation above microscale. FindingsThe analysis results indicate that both the decrease in substrate surface energy and the increase in gas oversaturation are more conducive to the nucleation and growth of surface nanobubbles, leading to larger stable sizes. The larger surface energy barriers result in the stronger pinning, which is beneficial for achieving stability of the pinned bubbles. The present model is able to reproduce the continual behaviors of the three-phase contact line during the nanobubble evolution, e.g., “pinning, depinning, slipping and jumping” induced by the nanoscale defects.

Effect of nano-scaled Al2O3 particles on dynamic recrystallization behavior and microstructure evolution of pure copper in hot deformation

The unusual dynamic recrystallization (DRX) behavior and microstructure evolution during compression deformation at 400–800 °C of a Cu–Al2O3 alloy were investigated herein. The calculation of activation energy (Q) and critical strain for DRX (εc), as well as the prediction of the volume fraction of DRX, are achieved through the construction of constitutive equations and a kinetic model of DRX. The nano-scaled Al2O3 particles are found to exert a significant pinning effect on dislocations and grain boundaries, significantly increasing the dislocation density. The Cu–Al2O3 exhibits a higher work hardening rate and stress compared to pure Cu under the same deformation conditions. The peak stresses of Cu–Al2O3 at 400 °C and 800 °C are 319.7 MPa and 155.4 MPa, respectively, 80.4 % and 243.1 % higher than those of pure Cu. The addition of nano-scaled Al2O3 particles reduces Q and εc of DRX, promoting the transition from low-angle to high-angle grain boundaries during high-temperature deformation. Additionally, distortion zones induced by Al2O3 particles as potential nucleation sites for DRX. While the addition of these particles promotes DRX of pure Cu, the initial DRX rate of Cu–Al2O3 is suppressed by the strong pinning effect of Al2O3 particles.

Solute Segregation and Pinning Effect on Lateral Twin Boundary in Magnesium

Deformation twinning creates a three-dimensional twin domain via the migration of forward, normal and lateral twin boundaries (TBs) with respect to twin shear direction, normal to twin plane and twin lateral direction. Solute segregation and pinning effect on the forward and normal TBs have been experimentally observed and demonstrated via atomistic simulations. Here, we conducted a comprehensive study of solute segregation and the pinning effect on the lateral TBs in Mg. First-principles density functional theory calculations were used to obtain the segregation and formation energies of 19 alloying elements in coherent regions of lateral TBs. Alloying elements with greater difference in atomic radius from Mg generally show more negative segregation energy. Moreover, alloying elements with good solubility are selected to demonstrate the pinning effect on a coherent interface. Ge, Ga, Y, Gd, La and Ca show negative segregation energy and solubility energy, indicating that these elements can form stable segregation and have a strong pinning effect at the lateral boundary. Molecular dynamics simulations revealed that solutes in coherent regions are more effective in pinning lateral TBs than those in misfit regions. The results provide insight into the selection of solute atoms for tailoring twinning behavior.

The influence of Sm[formula omitted]O[formula omitted] nanoparticles adding on some superconducting properties of Bi[formula omitted]Pb[formula omitted]Sr[formula omitted]Ca[formula omitted]Cu[formula omitted]O[formula omitted] ceramics

High-Temperature Superconductors Bi1.6Pb0.4Sr2Ca2Cu3O10+δ samples doped with Sm2O3 nanoparticles in different quantities (0.00, 0.02, 0.04 and 0.06), were synthesised. Solid state feedback technique was used to prepare the samples and then characterised. The morphology and structure of the specimens were deployed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) examination. The spectroscopy of the energy dispersive X-ray (EDX) experiment was utilised to obtain the elemental composition of the samples. Resistivity versus temperature measurement in DC mode was employed to estimate the critical transition temperature of each sample. XRD with the Rietveld refinement process revealed that Bi2223 and Bi2212 stages exist mutually in specimens with orthorhombic crystal systems. The lowest percentage of volume fraction associated with the Bi2223 phase belonged to the sample with x=0.06 nanoparticle samarium doped. It was detected that with rising samarium content the volume division of the Bi2223 phase decreases but the Bi2212 stage increases compared with the pristine specimen. SEM showed that the shrinkage of grain size occurs when the amount of nano-sized Sm was added to x=0.02 sample with lower inter-coupling among superconducting granules. This effect might be verified by SEM and TEM images. EDX exhibited some peaks related to Sm and other elements of the Bi2223 structure. These patterns confirm that all elements associated with the compounds were introduced into the Bi2223 matrix. The critical temperatures such as Tconset, TcPeak and Tczero decreased for Sm doped samples compared with the pure sample. Adding Sm2O3 nanoparticles causes rising calculated density and hole carrier concentration. These outcomes can be interpreted as the allocation of additional positive charges to the CuO2 planes. It is worth mentioning that the superb properties such as high-Tc, high Jc, strong flux pinning, and good thermal stability, for Bi2223 and high breakdown electric field, high dielectric constant, and large bandgap for Sm2O3 are the issues to motivate the author to dope Bi2223 with Sm2O3 NPs. In brief, the electrical, mechanical and structural properties of Sm2O3 NPs doped Bi2223 play the main role in the applications, which drive the investigations to emphasise the synthesis of superconducting samples.

Microstructural evolution, mechanical behavior, and deformation mechanisms of a lightweight Ti–Nb–Cr–V refractory high-entropy alloy at room and elevated temperatures

Refractory high-entropy alloys (RHEAs) have emerged as promising candidates for high-temperature applications owing to their distinctive mechanical properties. However, their limited tensile ductility and high density pose hurdles for further engineering utilization. In this study, we introduce a novel RHEA composition, Ti45Nb30Cr15V10 (at.%), distinguished by its reduced density (∼6.2 g/cm3), achieved through the assistance of CALPHAD (CALculation of PHAse Diagrams) modeling. The as-cast RHEA exhibits a single body-centered cubic (BCC) structure, demonstrating a tensile yield strength of ∼904 MPa along with a total elongation of ∼9.7 %. By employing cold rolling followed by recrystallized annealing (designated as the CRRA sample), we achieve notable enhancements in both strength and ductility. Specifically, the CRRA sample manifests an impressive tensile yield strength of ∼1010 MPa and a total elongation of ∼20.6 % at room temperature. Remarkably, even at an elevated temperature of 700 °C, the CRRA sample maintains notable strength, displaying a yield strength of ∼695 MPa. The observed dislocation behavior, transitioning from dual-system slip to multi-system slip, along with the intricate interactions of dislocation substructures (e.g., loops, tangles, networks, bands, and cells) and kink bands, are identified as the principal deformation mechanisms contributing to the exceptional tensile properties of the CRRA sample at room temperature. At 700 °C, the presence of wavy-slipping dislocations, induced by the strong pinning effect of component fluctuations, predominantly contributes to the strength of the CRRA sample. However, the emergence of Cr2(Ti, Nb, V) Laves phase at grain boundaries results in premature fracture. The extraordinary tensile properties exhibited by the CRRA sample at both room and elevated temperatures underscore its potential for advanced engineering applications.

The Contact Properties of Monolayer and Multilayer MoS2-Metal van der Waals Interfaces.

The contact resistance formed between MoS2 and metal electrodes plays a key role in MoS2-based electronic devices. The Schottky barrier height (SBH) is a crucial parameter for determining the contact resistance. However, the SBH is difficult to modulate because of the strong Fermi-level pinning (FLP) at MoS2-metal interfaces. Here, we investigate the FLP effect and the contact types of monolayer and multilayer MoS2-metal van der Waals (vdW) interfaces using density functional theory (DFT) calculations based on Perdew-Burke-Ernzerhof (PBE) level. It has been demonstrated that, compared with monolayer MoS2-metal close interfaces, the FLP effect can be significantly reduced in monolayer MoS2-metal vdW interfaces. Furthermore, as the layer number of MoS2 increases from 1L to 4L, the FLP effect is first weakened and then increased, which can be attributed to the charge redistribution at the MoS2-metal and MoS2-MoS2 interfaces. In addition, the p-type Schottky contact can be achieved in 1L-4L MoS2-Pt, 3L MoS2-Au, and 2L-3L MoS2-Pd vdW interfaces, which is useful for realizing complementary metal oxide semiconductor (CMOS) logic circuits. These findings indicated that the FLP and contact types can be effectively modulated at MoS2-metal vdW interfaces by selecting the layer number of MoS2.

High strength and high ductility Mg-Gd-Y-Zn-Zr alloys obtained by controlling texture and dynamic precipitation through LPSO phase structure of different initial morphologies

This paper investigated the effects of three different initial phase structures on the microstructure evolution and tensile properties of extruded Mg-Gd-Y-Zn-Zr alloy, using an extrusion ratio of 3.6. These three initial phase structures were obtained by heat treatment, which is narrow spacing long-period stacking ordered phase (LPSO) phase structure alloy (EN alloy), wide spacing LPSO phase structure alloy (EW alloy), and narrow spacing LPSO phase and β phase overlapping phase structure alloy (EO alloy). The dynamic recrystallization (DRX) and dynamic precipitation behavior of extruded alloys with different initial structures, as well as their strengthening and ductility mechanisms were studied in detail. After hot extrusion with a low extrusion ratio, the alloy exhibits a bimodal structure composed of undynamic recrystallization (UN-DRX) grains and dynamic recrystallization (DRX) grains with strong textures. The narrow-spacing LPSO phase structure inhibits DRX and dynamic precipitation, while both the wide-spacing LPSO phase structure and the overlapping phase structure alloys promote DRX and dynamic precipitation. The strength improvement is mainly due to the strong texture and internal dislocation pinning of the undynamic recrystallization zone (UN-DRX) and the high strengthening effect of the narrow spacing LPSO phase. Although the promotion of DRX improves grain boundary strengthening effect, it cannot make up for reducing the UN-DRXed grain strengthening effect. A lower volume fraction of β dynamic precipitation phase is beneficial for improving the ductility of the alloy.

Effect of Cu addition on the thermal conductivity and mechanical properties of Mg–Zn-xCu-Ce alloys

Thermal conductivity and mechanical properties of Mg–Zn-xCu-Ce alloys with different Cu contents under low extrusion temperature were systematically investigated in this work. The results shows that MgZnCu and Ce-rich (Mg, Zn, Cu, Ce) phase were formed in Mg–Zn-xCu-Ce alloys with high Cu content, which have significantly effect on the thermal conductivity and dynamic recrystallization (DRX). The distribution of grain morphology and LAGBs indicates that CDRX is the main mechanism. The addition of Cu element has an inhibitory effect on the DRX behavior, greatly refining the DRXed grains. After extrusion, a large amount of nano-phase is dispersed in the MZEC alloy, which has a strong pinning effect on dislocations. The formation of MgZnCu phase with high thermal conductivity sacrifices the solute atoms of Zn and Cu in α-Mg matrix, which leads to reduction of lattice distortion of Mg matrix, thereby ensuring high thermal conductivity of Mg–Zn–Cu–Ce ternary magnesium alloys. With the increase of Cu content, the strength and thermal conductivity of the alloy gradually increases. When the Cu content is 3.6 wt%, UTS (ultimate tensile strength), YS (yield strength), EL (elongation) and thermal conductivity are 350 MPa, 317 MPa,15.8% and 135 W/m∙K, respectively.

Oxygen solutes-regulated low temperature embrittlement and high temperature toughness in vanadium

The plasticity of body-centered cubic (BCC) metals is sensitive to interstitial trace impurities. Owing to high oxygen affinity, vanadium (V) shows a tendency of embrittlement with increasing oxygen concentration. However, how oxygen solutes affect the ductile-to-brittle transition (DBT) behavior of V remains unclear. In this study, we investigate the DBT behavior of V with different oxygen solute concentrations using small-punch test. As oxygen content increases, the DBT temperature (DBTT) rises incrementally accompanied by a widening of the semi-brittle transition zone. The reduction of the lower fracture energy plateaus indicates a classical low-temperature embrittlement, while the rising of the upper fracture energy plateaus manifests a remarkable high-temperature toughening. Below DBTT, owing to the strong pinning effect of oxygen-vacancy complexes on dislocations, only a limited number of slip systems were activated with very low dislocation density, and all screw dislocations are immobile. Above DBTT, owing to the intensive interactions between dislocation and oxygen-vacancy complexes, frequent dislocation cross-slips trigger multiple slip systems and accelerate dislocation multiplication and storage, all of which contribute to the high-temperature toughness. These findings clarify the effect of oxygen solute on the DBT of V and guide the design of high-performance refractory metals.

Twinning initiation from edge dislocations pinned by hydrogen atoms in bcc iron: A molecular dynamics study

Understanding how hydrogen affects the slip and twinning behaviors in metals is paramount for ensuring safe material use in a hydrogen environment and contributing to the development of hydrogen-resistant structural metals. Despite recent reports highlighting an increase in hydrogen-induced twinning in metals under applied deformations, the root case remains elusive. Here, we use molecular dynamics simulations to investigate how high hydrogen concentrations and shear direction affect edge-dislocation behavior in bcc iron. Our findings reveal that the pinning effect increases with hydrogen density along the dislocation line. This effect becomes more pronounced when shear is applied along the twinning direction. We demonstrate the nucleation of micro-twinning, characterized by a three atomic-layer thickness, originating from the dislocation under these conditions. The growth mechanism of this phenomenon aligns with Mahajan's model. Our findings identify the high shear stress as the primary driver for twinning, owing to the hydrogen's strong pinning effect.

Efficient Modulation of Schottky to Ohmic Contact in MoSi2N4/M3C2 (M = Zn, Cd, Hg) van der Waals Heterostructures.

A strong Fermi level pinning (FLP) effect can induce a large Schottky barrier in metal/semiconductor contacts; reducing the Schottky barrier height (SBH) to form an Ohmic contact (OhC) is a critical problem in designing high-performance electronic devices. Herein, we report the interfacial electronic features and efficient modulation of the Schottky contact (ShC) to OhC for MoSi2N4/M3C2 (M = Zn, Cd, Hg) van der Waals heterostructures (vdWHs). We find that the MoSi2N4/M3C2 vdWHs can form a p-type ShC with small SBH with the calculated pinning factor S ≈ 0.8 for MoSi2N4/M3C2 contacts. These results indicate that the FLP effect can be effectively suppressed in MoSi2N4 contact with M3C2. Moreover, the interfacial properties and SBH of MoSi2N4/Zn3C2 vdWHs can be effectively modulated by a perpendicular electric field and biaxial strain. In particular, an efficient OhC can be achieved in MoSi2N4/Zn3C2 vdWHs by applying a positive electric field of 0.5 V/Å and strain of ±8%.

Strengthening Mechanism and Damping Properties of SiCf/Al-Mg Composites Prepared by Combining Colloidal Dispersion with a Squeeze Melt Infiltration Process.

SiC-fiber-reinforced Al-Mg matrix composites with different mass fractions of Mg were fabricated by combining colloidal dispersion with a squeeze melt infiltration process. The microstructure, mechanical and damping properties, and the corresponding mechanisms were investigated. Microstructure analyses found that SiCf/Al-Mg composites presented a homogeneous distribution of SiC fibers, and the relative density was higher than 97% when the mass fraction of Mg was less than 20%; the fiber-matrix interface bonded well, and no obvious reaction occurred at the interface. The SiCf/Al-10Mg composite exhibited the best flexural strength (372 MPa) and elastic modulus (161.7 GPa). The fracture strain of the composites decreased with an increase in the mass fraction of Mg. This could be attributed to the strengthened interfacial bonding due to the introduction of Mg. The damping capacity at RT increased dramatically with an increase in the strain when the strain amplitude was higher than 0.001%, which was better than the alloys with similar composition, demonstrating a positive effect of the SiC fiber on improving the damping capacity of composite; the damping capacity at a temperature beyond 200 °C indicated a monotonic increase tendency with the testing temperature. This could be attributed to the second phase, which formed more strong pinning points and increased the dislocation energy needed to break away from the strong pinning points.

Observation of pinning and pinning evasion dynamics of a magnetic vortex core

An understanding of the dynamics of magnetic textures as they interact with defects in the host material is critical for proposed applications that depend on controlled translation of these magnetic textures. We report on the experimental observation of magnetic vortex core (VC) trajectories as they are affected by a potential energy landscape arising from defects in thin, permalloy disks. We first map the VC pinning landscape using equilibrium Kerr microscopy, and then use multiplexed time-resolved Kerr microscopy to track in-plane dynamics of a magnetic VC in response to a magnetic field pulse with ns time resolution, and several-nm spatial resolution. The initial position of the VC is set by applying a static magnetic field to shift the dynamics relative to the pinning landscape. We observe the expected spiral trajectory as the VC relaxes to equilibrium over several tens of nanoseconds. However, in the presence of strong pinning, we also observe pinning evasion as the VC trajectory is deflected due to the pinning potential, and enhanced damping as the vortex becomes pinned. We compare to a simple model based on the Thiele equation of motion to understand these results.

First‐Principles Study of Schottky Barrier Heights on Metal/4H‐SiC Polar Interfaces

4H‐SiC based devices have garnered significant interest within the realm of high‐voltage and high‐frequency electronic equipment. Schottky barrier heights (SBHs) play a pivotal role in determining the properties of metal/4H‐SiC contacts and holding significance for electrical performance of 4H‐SiC devices. Herein, the first‐principles method is utilized to investigate the interface properties between various metals (Sc, Mg, Zr, Ag, Al, Ru, Rh, Pd, Ni, Au, Ir, and Pt) and 4H‐SiC. The results reveal an approximate linear relationship between SBH and work function of these metals. Fermi‐level pinning factors are determined to be 0.27 and 0.32 for the Si‐face and C‐face interfaces, respectively. The disparity in pinning factors arises from polarization differences between the two interfaces, which stem from uneven net charge distribution on the Si‐face and C‐face. Meanwhile, the SBH values indicate a strong pinning effect, due to the charge transfer occurring at the metal/4H‐SiC interface. Through further analysis of layer density and differential charge density, the interatomic interaction and charge transfer between metal and SiC atoms are analyzed. This work offers fundamental insights into the structural changes in metal/4H‐SiC interfaces and provides valuable guidance in the potential prediction and optimization of device performance.