A novel solid-clad-by-liquid method was developed to form a 10-m long by 10-mm wide by 80-μm thick Ni–5 at.% W/Ni–9.3 at.% W/Ni–5 at.% W composite tape. Three deformation routes (cold rolling, cold rolling with intermediate annealing, and cold rolling combined with warm rolling) have been investigated in short Ni–5 at.% W/Ni–9.3 at.% W/Ni–5 at.% W composite substrate. To optimize the dynamic continuous annealing parameters for the long composite substrates, air-cooled and furnace-cooled annealing procedures were compared in short Ni–5 at.% W/Ni–9.3 at.% W/Ni–5 at.% W composite substrates. Improved cube texture of 98.7% in a 10-m long by 10-mm wide by 80-μm thick Ni–5 at.% W/Ni–9.3 at.% W/Ni–5 at.% W composite substrate was achieved via warm rolling deformation at 550 °C and two-step dynamic continuous annealing (750 °C for 1 h followed by 1200 °C for 1 h). The yield strength, Curie temperature, and saturation magnetization of 176 MPa, 324 K, and 18 emu/g, respectively, were obtained.

A quantum computer can outperform classical computers for certain tasks. The general challenge to realize a quantum computer is to solve decoherence, which is due to coupling of a quantum state with the local environment. One possible way to overcome decoherence is to use a topological quantum state. Topologically protected states are expected to have long coherence times. In a topological quantum computer, the information is carried by nonlocal Majorana states. Such states can be engineered in a semiconductor nanowire, which has strong spin–orbit interactions, coupled to a superconductor. The first signatures of Majorana states have been observed recently. In order to substantiate the existence of Majorana states and use them as qubits, an exchange—or braiding—operation of these states has to be performed. The current challenge is to improve the quality of the materials and interfaces. Recent progress toward improved Majorana signals using materials science advances is reviewed in this article.

We use irradiation with 50-MeV Cu-ions to create vortex pinning defects in high-temperature superconducting Y1Ba2Cu3O7-x coated conductors using a beam-rastering approach that allows for the uniform irradiation of large ample areas. Our samples contain barium zirconate nanorods as pre-existing vortex pinning defects. By irradiating the samples at angles of 0o, 15oand 30o from the crystallographic c-axis we explore the interplay between pre-existing and irradiation-induced pinning and find that irradiation at 30o leads to a moderate enhancement of Jc at 5 K at high fields (greater than 2 Tesla). In contrast, Jc was suppressed for all temperatures and fields for other angles of irradiation. Optimized particle irradiation procedures offer a way for improving the performance of high-temperature superconducting wires for use in high magnetic fields without the need for changing wire synthesis protocols.

As a pure element, bismuth is a semimetal which possesses several interesting physical properties, not all of them well understood. The recent discovery of superconductivity, as predicted by our group, and the increasing superconducting transition temperature as the pressure applied increases, are some examples of its particularities. Also, the fact that the amorphous phase is superconductive with a transition temperature several orders of magnitude larger than the crystalline at ambient pressure is unusual. These phenomena have also motivated our predictions for the transition temperatures of Bi-bilayers and the Bi-IV phase. When mixed with other elements, bismuth seems to contribute to the superconducting character of the resulting material. Here we study the binary copper-bismuth amorphous system which is known to superconduct in diverse compositions. Using ab initio molecular dynamics and the undermelt-quench method, we generate an amorphous structure for a 144-atom supercell corresponding to the Cu61Bi39 system. We calculate the electronic and vibrational densities of states for the amorphous system and estimate a superconducting critical temperature of 4.2 K for the amorphous state.

The superconductivity has a long history. One of the most recent discoveries is the superconductivity in the Fe- based family with anti- ferromagnetic state at ambient temperature. In this type of material, the transition to the superconductivity state was found in presence of different dopants. In this report we present the results of calculations of the cluster representing Ba4Fe5As8 in presence of Rh and Pd as dopants. The methodology of Embedded Cluster Method at the MP2 electron correlation level was employed. The population analysis showed two main features: the independence of charge density transfer from the spin density transfer and, the presence of orbitals with electron density but without spin density. The observed properties correspond to the RVB mechanism for the superconductivity transition proposed by Anderson for cuprates. This confirms our conclusions obtained in the same material doped by Co and Ni.

The doped iron arsenides present outstanding properties, one of them is an unconventional superconductivity, an unusual coexistence of superconductivity and magnetism. We calculated the electronic structure of the pure and Ni-doped BaF e2As2 by the embedded cluster method at the electron correlation level; the latter is calculated through the second- order Møller Plesset perturbation theory. For the doped clusters, we calculated the relaxation of the first and second neighbors of the impurity by optimizing their positions in the cluster. The total electronic density is analyzed through natural bond orbitals and the population of each atomic orbital (basis function) is determined; the robustness of this determination is tested comparing results obtained for the unrelaxed and relaxed cluster. The orbital population analysis uncovers some properties of magnetism and superconductivity in BaFe2As2. From our results, linear elasticity allows us to estimate the relaxation volume of Ni impurity.

While most papers on high-entropy alloys (HEAs) focus on the microstructure and mechanical properties for structural materials applications, there has been growing interest in developing high-entropy functional materials. The objective of this paper is to provide a brief, timely review on select functional properties of HEAs, including soft magnetic, magnetocaloric, physical, thermoelectric, superconducting, and hydrogen storage. Comparisons of functional properties between HEAs and conventional low- and medium-entropy materials are provided, and examples are illustrated using computational modeling and tuning the composition of existing functional materials through substitutional or interstitial mixing. Extending the concept of high configurational entropy to a wide range of materials such as intermetallics, ceramics, and semiconductors through the isostructural design approach is discussed. Perspectives are offered in designing future high-performance functional materials utilizing the high-entropy concepts and high-throughput predictive computational modeling.

The topological insulator/superconductor heterostructure is one of the most promising platforms to create and manipulate Majorana bound states. Here, we used molecular beam epitaxy to grow high-quality (Bi0.5Sb0.5)2Te3 films on Nb surfaces. To promote proper (Bi0.5Sb0.5)2Te3 film nucleation in the early growth stage, we developed a two-step growth method. Bi, Sb, and Te clusters were first evaporated at a low temperature of 180 °C, which is below the typical growth temperature and then annealed to form a crystalized passivation layer. Second, a standard (Bi0.5Sb0.5)2Te3 film was grown under the normal deposition temperature of 280 °C. We used reflection high-energy electron diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction to further characterize the (Bi0.5Sb0.5)2Te3 film and passivation layer quality. Finally, the top Nb film was laid down by magnetron sputtering at room temperature. The hetero-Nb/epitaxial (Bi0.5Sb0.5)2Te3/Nb stacks were further fabricated into micro-Josephson junctions and showed clear Josephson currents demonstrating an excellent material quality.

Previously known to form only under high pressure synthetic conditions, here we report that the T′-type 214-structure cuprate based on the rare earth atom Tb is stabilized for ambient pressure synthesis through partial substitution of Pd for Cu. The new material is obtained in purest form for mixtures of nominal composition Tb1.96Cu0.8Pd0.2O4. The refined formula, in orthorhombic space group Pbca, with a = 5.5117(1) Å, b = 5.5088(1) Å, and c = 11.8818(1) Å, is Tb2Cu0.83Pd0.17O4. An incommensurate structural modulation is seen along the a axis by electron diffraction and high resolution imaging. Magnetic susceptibility measurements reveal long-range antiferromagnetic ordering at 7.9 K, with a less pronounced feature at 95 K; a magnetic moment reorientation transition is observed to onset at a field of approximately 1.1 T at 3 K. The material is an n-type semiconductor.

Materials chemistry was in its infancy when I started my independent research efforts in India after returning from the United States in the late 1950s. I have investigated phase transformations of TiO2 and CsCl, and also carried out defect calculations. While working on rare-earth oxides, I made TbO2 and PrO2 by a simple solution route; this is probably an early example of chimie douce (soft chemistry). I started working on transition-metal oxides by building simple instruments, including a thermobalance and furnaces. In 1987, we were able to fully characterize the first liquid N2 superconductor (YBa2Cu3O7) using a home-built AC susceptometer. Oxides have been of great interest to me because of the variety of phenomena exhibited by them. I have studied various aspects of transition-metal oxides, including metal-insulator transitions, colossal magnetoresistance, and multiferroics. The last two decades have included research on synthesis, characterization, and properties of various nanomaterials, and in particular, two-dimensional nanosheets (graphene and its inorganic analogues). Two-dimensional sheets and other nanomaterials have been covalently cross-linked to derive new materials with novel properties. Work on water splitting and reduction of CO2, besides using aliovalent anion substitution to generate novel inorganics (Zn2NF in place of ZnO), has also been conducted.

In the present study, changes of iron content, brightness, particle size, mineralogy and paramagnetic properties of kaolins before and after superconducting high gradient magnetic separation (SHGMS) were investigated. The Fe2O3 contents of the feed decreased by 56% after 3.5T SHGMS with 1# steel wool, but higher magnetic intensity to 5.5T did not remove additional iron. The ISO brightness of the kaolin sample after SHGMS was improved from 56.9% to 76.7%. The D50 value of the magnetic rejects was 35% larger compared to the feed. Large particles might block the micro-pores in the steel wool matrix. Compared to the feed, the dark or red impurities significantly decreased in the non-magnetic product. Paramagnetic species in the kaolin sample were sensitive to SHGMS. The resonances at g = ~2.0 and g = 4.0 decreased significantly in the concentrate compared to the feed in the ESR spectra. Iron components in the non-magnetic product were more likely to be non-paramagnetic. The results are useful for understanding the SHGMS in kaolin treatment, and might be a guide for optimizing process parameters.

The oxygen ions in the high temperature superionic state of uranium dioxide (UO2) are known to be in an arrested or jammed state, exhibiting characteristic features of jammed kinetics such as low dimensional string-like ion hopping and dynamical heterogeneity (DH). This thermally-jammed state entails a configurational entropic cost. Using atomistic simulations and the 2PT method, we compute the solid-like (vibrational) and hard sphere-like (configurational) contributions to the total entropy across a temperature range of 1500 K to 2800 K that envelop both the onset of superionic conduction (2000 K) and the second order λ-transition (2610 K). To properly account for the thermally jammed state of the ions, we use an equation of state that is appropriate for the metastable fluid branch. Our simulation results are in excellent agreement with the entropy data extracted from specific heat experiments with a mean error of less than 2%.

Using a 72-atom supercell we report ab initio calculations of the electronic and vibrational densities of states for the bismuth (111) bilayers (bismuthene) with periodic boundary conditions and a vacuum of 5 Å, 10 Å and 20 Å. We find that the electronic density of states shows a metallic character at the Fermi level and that the vibrational density of states manifests the expected gap due to the layers. Our results indicate that a vacuum down to 5 Å does not affect the electronic and vibrational structures noticeably. A comparison of present results with those obtained for the Wyckoff structure is displayed. Assuming that the Cooper pairing potential is similar for all phases and structures of bismuth, an estimate of the superconducting transition temperature gives 2.61 K for the bismuth bilayers.

In this paper, we presented design specifications and operational test results of large-sized high temperature superconducting (HTS) magnets for Superconducting Induction Heater (SIH). HTS magnets were designed and fabricated with the metal insulation method. Critical currents of the HTS magnets were estimated by considering the angular dependency on the magnetic flux density of HTS tape. The characteristic resistance, the charging and discharging time were calculated and measured in the liquid nitrogen and the conduction cooling condition achieved with the 2nd stage GM cryo-cooler. The saturated temperature of the HTS magnet reached at 5.6 K. The performances of the large-sized HTS magnet including cooling and magnetic field characteristics were tested under the conduction cooling. These results were evaluated with those of finite element method analysis results. The characteristic analysis results of the large-sized HTS magnets will be applied for development of the commercial 300 kW SIH.

Fusion energy is one of the options to contribute to the energy demand of future generations without adding to global warming. In this paper, we present the status of fusion energy research on the basis of magnetic confinement.

Fusion energy is one of the options to contribute to the energy demand of future generations without contributing to global warming. In this paper, we present the status of fusion energy research on the basis of magnetic confinement. In France, the first fusion reactor ITER is under construction. Its success will be measured on the expectation to deliver 500 MW thermal power—a factor of 10 above the power to maintain the energy producing process. ITER is based on the tokamak concept. In addition, Wendelstein 7-X, an ambitious stellarator, has recently started operation. Both confinement concepts—the tokamak and the stellarator—will be discussed along with general topics regarding fusion technology, operational safety, fusion waste, possible electricity costs, and roadmaps toward a fusion reactor as a power source.

This paper presents experimental results on the synthesis of boron rich diamond-like carbon phases (BCx) obtained by high pressure sintering (s-BCx) and pulsed laser deposition (PLD-BCx). It has been shown that sintering of a mixture of a powder of micro-diamonds with a powder of boron in the toroid type high pressure device leads to the creation of s-BCx phase with a low resistivity, and high elastic moduli. The PLD-BCx film found to be rigid with the resistivity as low as that of best conductive boron–doped diamond films. It indicates that the presence of B atoms in a laser plasma leads to the formation of sp3 bonds in the material in the process of chemical sputtering. The combination of unique characteristics can be achieved by changing the ratio B/C.

Coupling superconductors to quantum Hall edge states is the subject of intense investigation as part of the ongoing search for non-abelian excitations. Our group has previously observed supercurrents of hundreds of picoamperes in graphene Josephson junctions in the quantum Hall regime. One of the explanations of this phenomenon involves the coupling of an electron edge state on one side of the junction to a hole edge state on the opposite side. In our previous samples, these states are separated by several microns. Here, a narrow trench perpendicular to the contacts creates counterpropagating quantum Hall edge channels tens of nanometres from each other. Transport measurements demonstrate a change in the low-field Fraunhofer interference pattern for trench devices and show a supercurrent in both trench and reference junctions in the quantum Hall regime. The trench junctions show no enhancement of quantum Hall supercurrent and an unexpected supercurrent periodicity with applied field, suggesting the need for further optimization of device parameters.

We report the structure and synthesis approach for obtaining a ceramic nanocomposite pellet comprising ∼50 nm-sized TaC nanoparticles. A mixture of Ta metal powder and the carbon precursor 1,2,4,5-tetraphenylethynyl benzene, pelletized by vacuum pressing at 131 MPa, on further thermal treatment with Ar at 1400 °C yields such a ceramic composite. On air oxidation, the TaC nanoparticles are converted to Ta2O5 nanoparticles at 760 °C. Hardness measurements revealed that the composite exhibited a global hardness in the range of 1.23–1.57 GPa. However, nanoindentation studies showed that, locally, hardness of the TaC nanoparticles (∼15 GPa) approached that of the densified TaC ceramic. Superconducting studies of the pellet consistently exhibited two transitions with T c values of 10 K and 8.5 K, respectively, that corresponded to bulk TaC and to a component of unknown origin. The results discuss the morphological and constitutional characterizations of the TaC nanoparticle-containing composite.

The development of new materials and improvements of existing ones are at the root of the spectacular recent developments of new technologies for synchrotron storage rings and free-electron laser sources. This holds true for all relevant application areas, from electron guns to undulators, x-ray optics, and detectors. As demand grows for more powerful and efficient light sources, efficient optics, and high-speed detectors, an overview of ongoing materials research for these applications is timely. In this article, we focus on the most exciting and demanding areas of materials research and development for synchrotron radiation optics and detectors. Materials issues of components for synchrotron and free-electron laser accelerators are briefly discussed. The articles in this issue expand on these topics.

The oxide interface SrTiO3/LaAlO3 supports a 2D electron liquid displaying superconductivity and magnetism, while allowing for a continuous control of the electron density using a gate. Our recent measurements have shown a similar surprising nonmonotonic behavior as function of the gate voltage (carrier density) of three quantities: the superconducting critical temperature and field, the inverse Hall coefficient, and the frequency of quantum oscillations. While the total density has to be monotonic as function of gate, the last result indicates that one of the involved bands has a nonmontonic occupancy as function of the chemical potential. We show how electronic interactions can lead to such an effect, by creating a competition between the involved bands and making their sturcture non-rigid, and thus account for all these effects. Adding Fock terms to our previous Hartree treatment makes this scenario even more generic.