Boride Superconductor Research Articles

High-Throughput Screening for Boride Superconductors.

A high-throughput screening using density functional calculations is performed to search for stable boride superconductors from the existing materials database. The workflow employs the fast frozen-phonon method as the descriptor to evaluate the superconducting properties quickly. Twenty-three stable candidates were identified during the screening. The superconductivity was obtained earlier experimentally or computationally for almost all found binary compounds. Previous studies on ternary borides are very limited. Our extensive search among ternary systems confirmed superconductivity in known systems and found several new compounds. Among these discovered superconducting ternary borides, TaMo2B2 shows the highest superconducting temperature of ∼12 K. Most predicted compounds were synthesized previously; therefore, our predictions can be examined experimentally. Our work also demonstrates that the boride systems can have diverse structural motifs that lead to superconductivity.

Disordered MgB[formula omitted] superconductor critical temperature modeling through regression trees

Magnesium boride superconductors are promising candidates in high energy physics applications. These superconductors have several advantages as compared to other high temperature superconductors, such as the absence of weaklinks in grain boundaries, abundant availability of raw materials, simple wire fabrication process, and increased isotropy in microstructure and material performance. Critical temperature, Tc, is the most critical parameter in superconductor characterizations. Various factors have impacts on Tc, including the chemical doping, irradiation, and synthesis conditions. It has been shown that disorders in the crystal structure lead to changes in normal state resistivities and Tc, which are correlated with each other. Here, the regression tree model is developed to predict Tc of disordered magnesium boride superconductors through room temperature resistivities. This modeling approach manifests a high degree of accuracy and stability, contributing to efficient low-cost estimations of critical temperature and understandings of disorder and superconductivity in MgB2 superconductors.

Beneficial Impact of Excess Mg on Flux Pinning in Bulk MgB2 Synthesized with Ag Addition and Carbon Encapsulated Boron

Silver addition has been known to improve mechanical and superconducting performance of bulk magnesium boride (MgB2) superconductor synthesized via solid state sintering. While formation of pinning phases and impurities such as Ag–Mg phases and MgO, respectively, responsible for high performance, part of the Mg in initial mixture will be expected to be consumed by silver. In this work, the authors add varied amounts of Mg systematically such as x: 2 (while x = 1.05, 1.075, 1.1, 1.125, 1.15) ratio of Mg:B instead of usual stoichiometric ratio of 1:2. To obtain high superconducting properties, the authors use carbon encapsulated boron (1.5% carbon) along with 4 wt% Ag. X‐ray diffraction analysis shows the presence of Ag–Mg phases and minute amount of MgO. Superconducting quantum interference device (SQUID) measurements indicate that high irreversibility field (4.76 T) and large Jc of 520, 440, and 347 kA cm−2 at 10, 15, and 20 K, respectively, at self‐field was exhibited in sample with x = 1.075. Flux pinning force studies are done to analyze the effect of secondary phases formed. All results analyzed explain the improved critical current performance based on nanometer‐sized Ag–Mg particles in the final product.

Progress in the research of copper-oxide superconductors

Since H·Carvalin·Onnesse discovered the superconductivity of mercury in 1911, we have made progress in the research of the superconductor and the superconductor have evolved from single element, alloy to complex compounds with multiple elements.With the development of the research about new superconducting materials, the research of iron based superconductors, copper-oxide superconductor and magnesium boride superconductor is the latest research trend. So far the proved highest superconducting transition temperature of copper-oxide superconductor is 130 K under normal pressure and could reach more than 160 K under high pressure. Based on the experience accumulated in past decades, we propose some general introduction about the main structure type, the superconducting principle and the application of copper-oxide superconductor.It is expected that a positive effect would be made in the research of copper-oxide superconductor.
 Background: Since H·Carvalin·Onnesse discovered the superconductivity of mercury in 1911, we have made progress in the research of the superconductor and the superconductor have evolved from single element, alloy to complex compounds with multiple elements.
 Aim: The purpose of this paper is to explain the differences between copper oxide superconductors and conventional superconductors and their superconducting mechanism.
 Methods: The superconducting mechanism and structure of copper oxide superconductors were analyzed by means of literature investigation, conceptual analysis and comparative study.
 Results: In this paper, the different structure forms of copper oxide are analyzed, and its superconducting mechanism is described in detail. The applications of several main copper oxide superconductors are introduced.
 Conclusion: Based on the experience accumulated in past decades, we propose some general introduction about the main structure type, the superconducting principle and the application of copper-oxide superconductor.It is expected that a positive effect would be made in the research of copper-oxide superconductor.

Probing the superconducting ground state of the rare-earth ternary boride superconductors RRuB2 ( R= Lu,Y) using muon-spin rotation and relaxation

The superconductivity in the rare-earth transition metal ternary borides $R$RuB$_2$ (where $R$ = Lu and Y) has been investigated using muon-spin rotation and relaxation. Measurements made in zero-field suggest that time-reversal symmetry is preserved upon entering the superconducting state in both materials; a small difference in depolarization is observed above and below the superconducting transition in both compounds, however this has been attributed to quasistatic magnetic fluctuations. Transverse-field measurements of the flux-line lattice indicate that the superconductivity in both materials is fully gapped, with a conventional s-wave pairing symmetry and BCS-like magnitudes for the zero-temperature gap energies. The electronic properties of the charge carriers in the superconducting state have been calculated, with effective masses $m^*/ m_\mathrm{e} = $ $9.8\pm0.1$ and $15.0\pm0.1$ in the Lu and Y compounds, respectively, with superconducting carrier densities $n_\mathrm{s} = $ ($2.73\pm0.04$) $\times 10^{28}$ m$^{-3}$ and ($2.17\pm0.02$) $\times 10^{28}$ m$^{-3}$. The materials have been classified according to the Uemura scheme for superconductivity, with values for $T_\mathrm{c}/T_\mathrm{F}$ of $1/(414\pm6)$ and $1/(304\pm3)$, implying that the superconductivity may not be entirely conventional in nature.

ChemInform Abstract: Fragment‐Based Design of NbRuB as a New Metal‐Rich Boride Superconductor.

AbstractThe title compound is synthesized by arc‐melting of the elements and characterized by powder and single crystal XRD, electrical resistivity and magnetic susceptibility measurements, and by TB‐LMTO‐ASA calculations.

Fragment-Based Design of NbRuB as a New Metal-Rich Boride Superconductor

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTFragment-Based Design of NbRuB as a New Metal-Rich Boride SuperconductorWeiwei Xie, Huixia Luo, Kristen Baroudi, Jason W. Krizan, Brendan F. Phelan, and Robert J. Cava*View Author Information Department of Chemistry, Princeton University, Princeton, New Jersey 08540, United States*E-mail: [email protected]Cite this: Chem. Mater. 2015, 27, 4, 1149–1152Publication Date (Web):January 27, 2015Publication History Received4 December 2014Revised25 January 2015Published online5 February 2015Published inissue 24 February 2015https://doi.org/10.1021/cm504449sCopyright © 2015 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1061Altmetric-Citations25LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (2 MB) Get e-AlertsSupporting Info (2)»Supporting Information Supporting Information SUBJECTS:Crystal structure,Heat capacity,Superconducting transition,Superconductivity,Superconductors Get e-Alerts

Angle-resolved photoemission spectroscopy of Co-based boride superconductor LaCo1.73Fe0.27B2

We have performed angle-resolved photoemission spectroscopy of Co-based boride superconductor LaCo${}_{1.73}$Fe${}_{0.27}$B${}_{2}$ (${T}_{c}=4.1$ K), which is isostructural to the 122-type Fe-pnictide superconductor with the pnictogen atom being replaced with boron. We found that the Fermi level is located at a dip in the density of states (DOS) in contrast to Co-pnictide ferromagnets. This reduction in DOS together with the strong Co 3$d$-B 2$p$ covalent bonding removes the ferromagnetic order and may cause the superconductivity. The energy bands near the Fermi level show higher three dimensionality and a weaker electron-correlation effect than those of Fe pnictides. The Fermi surface topology is considerably different from that of Fe pnictides, suggesting the difference in the superconducting mechanism between boride and pnictide superconductors.

Electronic Structures and Density of States of Borides AB(A=Zr,Hf,Nb and Ta)

. The accurate first-principle method was used to calculate the electronic structures of the four boride superconductors. Their DOS (the density of states), band structures as well as their specific electronic structures were discovered. It was found that they all had a metallic band crossing the Fermi surface on the Γ point. These characters made their attribute of superconductivity and the interstics of NbB was the least which resulted in its higher Tc than the others.

Microscopic properties of vortex states inYB6probed by muon spin rotation

The local magnetic field distribution $B(\mathbf{r})$ in the mixed state of a boride superconductor, $\mathrm{Y}{\mathrm{B}}_{6}$, is studied by muon spin rotation $(\ensuremath{\mu}\mathrm{SR})$. A comparative analysis using the modified London model and Ginzburg-Landau (GL) model indicates that the latter exhibits a better agreement with $\ensuremath{\mu}\mathrm{SR}$ data at higher fields and thus demonstrating the importance of reproducing the field profile near the vortex cores when the intervortex distance becomes closer to the GL coherence length. The temperature and field dependence of the magnetic penetration depth $(\ensuremath{\lambda})$ does not exhibit any indications of the nonlocal effect or of low-lying quasiparticle excitation. This suggests that the strong coupling of electrons to the rattling motion of Y ions in the boron cage, as suggested by bulk measurements, induces a conventional superconductivity with isotropic $s$-wave pairing. Considering the present results, a review is provided for probing the anisotropy of the superconducting order parameters by the slope of $\ensuremath{\lambda}$ against the field $(\ensuremath{\eta}\ensuremath{\propto}d\ensuremath{\lambda}∕dH)$.

Temperature dependences of the upper critical field and the Ginzburg–Landau parameter of Li2Pd3B from magnetization measurements

We present temperature dependences of the upper critical magnetic field Hc2 and the Ginzburg–Landau parameter κ for a ternary boride superconductor Li2Pd3B obtained from magnetization measurements. A specially developed scaling approach was used for the data analysis. The resulting Hc2(T) curve turns out to be surprisingly close to predictions of the BCS theory. The magnetic field penetration depth λ, evaluated in this work, is in excellent agreement with recent muon-spin-rotation experiments. We consider this agreement as an important proof of the validity of our approach.

Magnetization measurements on Li2Pd3B superconductor

Magnetization in dc magnetic fields and at different temperatures has been measured on the antiperovskite Li2Pd3B with a cubic structure composed of distorted Pd6B octahedrons. This material was recently found to exhibit superconductivity at 7–8K. The critical fields Hc1(0) and Hc2(0) are determined to be 135Oe and 4T, respectively. Critical current density, scaling of the pinning force within the Kramer model, and irreversibility field data are presented. Several superconductivity parameters were deduced: Coherence length ξ=9.1nm, penetration depth λ=194nm, and Ginzburg–Landau parameter κ=21. The material resembles other boride superconductors from the investigated points of view.

MÖSSBAUER STUDIES OF TERNARY SUPERCONDUCTORS

Moessbauer studies of the ternary Chevrel phase and rare earth rhodium boride superconductors have been made. Anomalous phonon properties at the Sn site in SnMo/sub 6/S/sub 8/, SnMo/sub 6/Se/sub 8/, and La/sub 0/ /sub 98/Sn/sub 0/ /sub 02/Mo/sub 6/Se/sub 8/ have been investigated. Studies of polarization of conduction electrons at the site of the magnetic ion have been made by means of the /sup 151/Eu Moessbauer effect in Eu/sub x/Sn/sub 1-x/Mo/sub 6/S/sub 8/ and the effects of such polarization on superconducting properties discussed. The Moessbauer effect in /sup 166/Er has been used to investigate the electronic ground state in the ternary compound ErRh/sub 4/B/sub 4/ both in the superconducting and magnetically ordered states.