National Institute for Materials Science

This paper reports numerical analysis results of AC losses when a rotating magnetic field is applied to a MgB ₂ wire. The losses include coupling losses, hysteresis losses, and eddy current losses. The H-ϕ formulation is used for the finite element analysis for the loss analysis of the electromagnetic phenomena in the MgB2 wire. And the losses are calculated when the contact resistivity and contact length between MgB ₂ wires are changed. The given rotational frequencies are 25 Hz and 50 Hz, and the flux density amplitude of the applied magnetic field is 0.01 T. As a result, it is shown that the coupling losses are inversely proportional to the contact resistance. And it is also found that the coupling losses are proportional to the square of the contact length. These tendencies can be explained by the theoretical formula for coupling losses.

Developing bifunctional electrocatalysts with superior oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) activity and high durability are crucial for rechargeable metal‐air batteries. Transition‐metal‐based layered double hydroxides (LDHs) are promising in the application as cost‐effective and high‐performance air cathodes. Herein, hierarchical composites of Zeolitic imidazolate framework (ZIF)‐derived CoNiFe LDH nanocages in situ grown on silver nanowires (Ag NWs) are synthesized as carbon‐free bifunctional oxygen electrocatalysts. The hollow structure of LDH and heterointerface with conductive Ag substrate not only maximizes exposure of active sites but also ensures effective electron transfer. In addition, the hybridization with Ag induces structural disorder and unsaturated coordination in the LDH shells, thereby enhancing intrinsic catalytic activity. Theoretical calculations reveal that the incorporation of Ag species can tune the electronic states and reduce the reaction barriers of OER and ORR. As a result, CoNiFe LDH@Ag NWs exhibit a bifunctional overpotential of 0.63 V. Applied as a carbon‐free cathode in a zinc‐air battery, CoNiFe LDH@Ag NWs yield a high specific capacity of 808 mAh g⁻¹ and long cycling stability up to 300 h. This work provides new insight into the design of LDH hierarchical structure for efficient and durable electrocatalysts.

Producing future fuels, such as green hydrogen, using less external energy input is a key factor in making such fuels truly environmentally friendly. In addition, the requirement of reducing the amount of catalyst used per mass of fuel produced is key for resource stability, particularly for platinum group metals which dominate such catalysis fields. Herein, a proof‐of‐principle approach is demonstrated to achieve both targets through piezo‐electro‐catalysis from chemically stable, flexible, fluoropolymers. Highly polarized MXene‐poly(vinylidene‐difluoride)‐co‐(trifluoro‐ethylene) interfaces, with an embedded platinum mesh electrode, are shown to decrease the onset overpotential of the mesh by 200 mV, thus lowering the overall energy and Pt required to produce a given mass of hydrogen. The simple approach used herein can be applied to other, advanced catalysts, to boost performance and efficiency.

Spin–valley properties in two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDCs) has attracted significant interest due to the possible applications in quantum computing. Spin–valley properties can be exploited in TMDC quantum dot (QD) with well-resolved energy levels. This requires smaller QDs, especially in material systems with heavy carrier effective mass e.g. TMDCs and silicon. Device architectures employed for TMDC QDs so far have difficulty achieving smaller QDs. Therefore, an alternative approach in the device architecture is needed. Here, we propose a multilayer device architecture to achieve a gate-defined QD in TMDC with a relatively large energy splitting on the QD. We provide a range of device dimensions and dielectric thicknesses and its correlation with the QD energy splitting. The device architecture is modeled realistically. Moreover, we show that all the device parameters used in modeling are experimentally achievable. These studies lay the foundation for future work toward spin–valley qubits in TMDCs. The successful implementation of these device architectures will drive the technological development of 2D materials-based quantum technologies.

The search for anyons, quasiparticles with fractional charge and exotic exchange statistics, has inspired decades of condensed matter research. Quantum Hall interferometers enable direct observation of the anyon braiding phase via discrete interference phase jumps when the number of encircled localized quasiparticles changes. Here, we observe this braiding phase in both the ν = 1/3 and 4/3 fractional quantum Hall states by probing three-state random telegraph noise (RTN) in real-time. We find that the observed RTN stems from anyon quasiparticle number n fluctuations and reconstruct three Aharonov-Bohm oscillation signals phase shifted by 2π/3, corresponding to the three possible interference branches from braiding around n (mod 3) anyons. Our methods can be readily extended to interference of non-abelian anyons.

The high susceptibility of the Ti–6Al–2Sn–4Zr–6Mo wt pct (Ti6246) alloy to microstructural changes stands as a challenge when processed by the laser powder bed fusion (LPBF) technology. However, leveraging the capabilities of the LPBF process to successfully control the microstructure (and/or crystallographic texture) of the Ti6246 could improve mechanical properties, particularly at elevated temperatures. In this study, the creep performance (at 500 °C) of Ti6246 fabricated from three different LPBF processing conditions and heat-treated (HT) at 885 °C were investigated. In the as-built state, all the LPBFed-Ti6246 exhibited columnar microstructures with crystallographic lamellar-like microstructure (CLM), a near-single crystal-like microstructure (SCM), and polycrystalline microstructure (PCM) textures, respectively. At low applied stresses (100–300 MPa), diffusional creep was the dominant deformation mechanism and its resistance depended on grain size. The reference β-forged-HT Ti6246, characterized by large equiaxed grains, exhibited the lowest strain rate compared to the columnar microstructure of SX1 (CLM)-HT, SX2 (SCM)-HT, and SX3 (PCM)-HT. Conversely, dislocation slip governed deformation at high applied stresses (400–580 MPa) and its efficacy depended on the α/β interfaces in the microstructures. Disjointed columnar grains in SX1 (CLM)-HT and the deformation of the polycrystalline grains in SX3 (PCM)-HT indicated that the melt pool boundaries were unstable in the LPBFed-Ti6246. SX2 (SCM)-HT exhibited the longest creep life due to the relatively stable melt pool boundaries and the near < 001 > SCM crystallographic texture parallel to the applied stresses. Shallow ductile dimples and tears and the observation of laser scan tracks characterized the fracture surfaces of the LPBFed-Ti6246. These indicated that failure occurred by intergranular ductile fracture resulting from the formation of microvoids at the melt pool boundaries.

Methylammonium chloride (MACl) enhances the performance of Dion-Jacobson quasi-2D tin perovskite solar cells by suppressing low-dimensional phases and defects. The addition of an optimal amount of MACl (20 mol%) improves...

Negatively charged nitrogen vacancy (NV⁻) centres in diamond crystals are promising colour centres for high-sensitivity quantum sensors. A long dephasing time (T2* > 10 μs) is essential for achieving increased sensitivity and higher uniformity of T2* in millimetre-scale diamond is strongly desired for femto-tesla weak magnetic field detection. High uniformity of T2* for NV⁻ centres is achieved herein. The median value of T2*, <T2*>, in the ¹²C-enriched high-pressure, high-temperature (HPHT) grown diamond with a nitrogen concentration of 1.3 ± 0.4 ppm is 4.5 μs. The variance of T2* is only 10% over a millimetre-scale region (1.1 × 1.1 mm²) within the 0.4 mm thick {111} growth sector. <T2*> is ~2/3 times the value limited by the dipole-dipole interaction from the electron-spin bath of nitrogen impurities, suggesting that the residual strain gradient in the HPHT diamond crystal partially limits T2*. Reducing the strain gradient in diamond crystals provide a pathway to achievement of high sensitivity magnetometry using NV quantum sensing.

Droplet coalescence is ubiquitous in nature, and its regulation is significant in industrial processes and biomedical applications. While bare droplets suddenly coalesce in contact, the droplets covered with liquid‐repellent particles to form “liquid marbles (LMs)” are not. Previously, the external stimuli‐responsive breakage of the particle layer enables the regulation of the coalescence timing. However, preprogramming the coalescence timing of droplets without stimuli is challenging. In this work, LMs that break the particle layer in preprogrammed time are reported. The particles have a core wettable site and are tethered with a low‐wettability flexible molecular chain, which gradually increases wettability with time. The time‐dependent wettability variation is observed because of the differences in the adaptation of the molecular chain; thus, it is repeatedly available, and its speed is controllable by chain length. The formed LMs expose bare droplet surfaces in preprogrammed timing, which enables the modulation of coalescence timing from 2 to 45 min without relying on external stimuli. Moreover, the additivity of the particles enables the fine‐tuning of the coalescence time with ≈1 min resolutions. Further, the contact of several LMs with different adaptation times enables cascade droplet coalescence, opening a new route for droplet manipulation.

Magnetic anisotropy plays a crucial role in determining the critical behavior and phase transitions in two-dimensional magnetic systems. It is also required for the design of thin-film spintronic devices. Despite its significance, sensing extremely weak anisotropy has proven challenging in van der Waals antiferromagnetic/ferrimagnetic materials. Here, we first employ simulations of micromagnetic energy function in few-layer easy-plane antiferromagnetic systems with a weak additional uniaxial anisotropy and unveil an intriguing even–odd effect closely linked to low-field spin–flop behaviors. We further perform tunneling magneto-conductance measurements on a model 2D antiferromagnetic insulator, CrCl 3 , exhibiting near-ideal easy-plane anisotropy. The magnetic field-controlled tunneling current at low temperature aligns well with simulated in-plane anisotropic spin-configuration, providing direct experimental evidence for detecting magnetic anisotropy field around 1 mT. Our work creates opportunities for finely characterizing magnetic structures and behaviors in 2D antiferromagnetic/ferrimagnetic systems, with potential applications in spintronics such as data storage and magnetic sensing.

Shape‐persistent macrocycles with confined inner spaces have gained significant interest due to their unique properties and potential applications in gas/molecular recognition, nanoscale templates, and nanoelectronics. In this study, we present an efficient synthesis of macrocycles containing anthracene units through reversible boronic ester formation between 1,2‐diols and boronic acids. These template‐free macrocycles exhibited diverse internal cavities ranging from 11 Å to 20 Å and readily crystallized in solution and on solid substrates. Powder X‐ray diffraction analysis revealed that the crystallinity remained after solvent removal. Single crystal X‐ray analysis provided detailed insights into the molecular geometry and packing structure. Notably, a macrocycle with phenyl linkers resembles a pseudo‐nanocapsule, as the bulky substituents on both sides of the macrocycles prevented the cavity filling by neighbouring molecules. Consequently, the crystalline powders of the macrocycle with phenyl linkers maintained its crystallinity even after annealing, likely resulting in the highest N2 gas adsorption properties among synthesized macrocycles. This work highlights a robust synthesis strategy for macrocycles, broadening their potential for advanced applications and enabling self‐assembled nanoarchitectures.

Antiferromagnets with broken time-reversal symmetry, such as Mn3Sn, have emerged as promising platforms for exploring topological and correlated electron physics. Mn3Sn is known to show two magnetic phase transitions: a non-collinear inverse triangular antiferromagnetic (IT-AFM) spin configuration is formed below its Néel temperature (TN ≅ 420 K), whereas at T1 that usually locates below room temperature, it transits to an incommensurate spin state. Accordingly, intriguing properties such as a strong anomalous Hall effect, observed from TN to T1, disappear below T1, limiting its utility at low temperatures. While bulk Mn3Sn has been extensively studied, the magnetic phase transitions and their tunability in thin films remain largely unexplored. Here, we investigate the magnetic and magneto-transport properties of Mn3+xSn1−x epitaxial thin films prepared by magnetron sputtering, systematically varying the Mn–Sn composition. Our results reveal that intrinsic alloying with Mn provides us with a handle to tune T1, with the IT-AFM phase stabilized down to liquid helium temperatures for x > 0.15. From a magnetic phase diagram for epitaxial thin films, we also find a consistent magnetic anomaly ∼55 K below TN, accompanied by thermal hysteresis. Furthermore, the reduction in TN in thin films relative to bulk values is shown to correlate with lattice parameter changes. These findings extend the accessible temperature range for Mn3Sn’s topological properties, paving the way for novel applications and further investigations into the interplay of spin, lattice, and electronic degrees of freedom in thin-film geometries.