Magnetic-field-induced orientation of superconducting<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Mg</mml:mi><mml:msub><mml:mi mathvariant="normal">B</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>crystallites determined by x-ray diffraction

Li, J.; Vaknin, David; Bud’ko, Sergey L.; Canfield, Paul C.; Pal, D.; Eskildsen, M. R.; Islam, Zahirul; Kogan, V. G.

doi:10.1103/physrevb.74.064502

Cited by 3 publications

(3 citation statements)

References 23 publications

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“…No indications for different λ and ξ anisotropies were found in torque measurements [75,99]. In particular the predicted sign reversal of the torque [83,100] was never observed [75,99,101]. One common (field-dependent) anisotropy for λ and ξ was assumed for the calculations presented in this paper (figures 1-6).…”

Section: The Influence Of the π Bandmentioning

confidence: 70%

Magnetic properties and critical currents of MgB₂

Eisterer

2007

Supercond. Sci. Technol.

297

294

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This review focuses on the superconducting properties of MgB2 that are relevant for power applications. The reversible mixed state parameters are the most important, since they define the limiting conditions for loss-free currents: the transition temperature, the upper critical field and the depairing current. They also determine the flux pinning energy, the pinning force and the elastic properties of the flux line lattice and, therefore, strongly influence the critical current densities. The magnetic properties of magnesium diboride are anisotropic and influenced by the two different energy gaps of the σ- and π-bands. Whereas the transition temperature could not be enhanced significantly during the past five years, the upper critical field was considerably increased by impurity scattering or doping. Flux pinning is very weak in MgB2 single crystals and was only improved by irradiation techniques so far. In polycrystalline samples, grain boundary pinning seems to play the dominant role. High critical currents close to the theoretical limit were found in c-axis oriented thin films. The anisotropy of the upper critical field strongly reduces the critical currents in untextured MgB2 at high magnetic fields, where the supercurrents become highly percolative, since not all grains are superconducting anymore. The performance of polycrystalline wires and tapes was significantly improved during the past few years by increasing the upper critical field and by reducing its anisotropy. Pinning seems to be nearly optimized in many forms of this material, but the connectivity between the grains might be further improved.

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Section: The Influence Of the π Bandmentioning

confidence: 70%

Magnetic properties and critical currents of MgB₂

Eisterer

2007

Supercond. Sci. Technol.

297

294

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“…For Ni 2 P, Ni 3 P 2 (0001) was selected to investigate the reaction due to its higher stability. [34] The corresponding values are: 0.93 (0.20), 1.00 (À 0.04), 1.05 (0.49), and 1.09 (À 0.05) eV. The situation on Ni 3 P 4 (0001) is slightly different.…”

Section: Reaction Mechanismmentioning

confidence: 94%

Ensemble Design in Nickel Phosphide Catalysts for Alkyne Semi‐Hydrogenation

et al. 2018

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Modification of transition metals with p‐block elements is known to be effective to tune the ensemble characteristics of catalysts for the semi‐hydrogenation of alkynes. To further explore this approach, here we prepare two nickel phosphides, namely Ni2P and Ni5P4. Assessment in the semi‐hydrogenation of 1‐hexyne and 2‐methyl‐3‐butyn‐2‐ol shows that the phosphides present higher rate and selectivity than unmodified nickel catalysts. While no activity and selectivity differences are displayed in the semi‐hydrogenation of 1‐hexyne over Ni2P and Ni5P4, in the case of 2‐methyl‐3‐butyn‐2‐ol a higher rate and lower selectivity to 2‐methyl‐3‐buten‐2‐ol are observed over Ni2P. Density functional theory reveals that the hydroxyl group facilitates the reaction, but also increases the barrier for product desorption. Detailed analyses of the ensemble show the potential of phosphorus to create spatially‐isolated nickel trimers that surpass the performance of unmodified nickel, but also its limited ability to modulate the electronic properties and related binding energies of organic intermediates, which is key to preventing undesired side reactions.

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“…KEYWORDS : nickel phosphide, single crystal surface, scanning tunneling microscope, surface structure に示す。Ni2P 結晶は Fe2P 型の六方晶系であり，2次元ユニットセルの組成が Ni3P1 と Ni3P2 となる二つの構造が[0001]方向に沿って交互に積み重なってできあがっている 11) 。Ni3P1 構造と Ni3P2 構造中の Ni は，それぞれ，Nisp と Nit からなっている。Ni2P(0001)単結晶表面を中心に表面科学的研究が行われている 4),[11][12][13][14][15][16][17][18][19] 。特に，低速電子線回折(Low Energy Electron Diffraction, LEED) および走査型トンネル顕微鏡(Scanning Tunneling Microscopy, STM)による表面構造が調べられている 12-15) 。 Moula らは，Ni2P(0001)単結晶表面の STM を測定し， STM 画像にあらわれる輝点を P 原子に帰属し， (1×1) 構造には Ni3P1 構造と Ni3P2 構造の両方(Ni3P1 構造の方が多め)が存在すると述べている。この帰属は，Ni2P (0001)単結晶表面の密度汎関数理論(Density Functional Theory, DFT)計算 16) により支持された。しかしながら，…”

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Reactivity of Ni2P(10-10) Surface for NO Evaluated by STM

健太郎¹,

寛子²,

達³

et al. 2014

Journal of The Surface Science Society of Japan

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In order to understand relation between surface structure and catalytic activity, we studied the Ni2P (1010) surface using scanning tunneling microscopy (STM). Atomic scale STM images of c(2×4) structure and (1×1) structure were obtained after annealing the sample at 653 K (denoted as surface structure I). The area of c (2×4) structure was decreased by the NO exposure at 573 K. A c(2×4) structure together with c(2×2) structure was obtained after the repeated sputtering-annealing treatments and reactions, which was called as surface structure II. Contrary to the surface structure I, this surface didnʼt change its structure by the NO exposure at 573 K. Since the (1×1) structure on the surface structure I had exposed Nit (tetrahedral Ni) and Nisp (square pyramid Ni) pairs, NO might be activated and destroy the c(2×4)structure, while c(2×2) structure on the surface structure II had no exposed Nit and Nisp pair so that surface structure II was less reactive. The removal of the surface P atoms is important for the activation of the Ni2P surface.

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Magnetic-field-induced orientation of superconductingMgB2crystallites determined by x-ray diffraction

Cited by 3 publications

References 23 publications

Magnetic properties and critical currents of MgB₂

Magnetic properties and critical currents of MgB₂

Ensemble Design in Nickel Phosphide Catalysts for Alkyne Semi‐Hydrogenation

Reactivity of Ni2P(10-10) Surface for NO Evaluated by STM

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Magnetic-field-induced orientation of superconductingMgB2crystallites determined by x-ray diffraction

Cited by 3 publications

References 23 publications

Magnetic properties and critical currents of MgB2

Magnetic properties and critical currents of MgB2

Ensemble Design in Nickel Phosphide Catalysts for Alkyne Semi‐Hydrogenation

Reactivity of Ni2P(10-10) Surface for NO Evaluated by STM

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Product

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Magnetic properties and critical currents of MgB₂

Magnetic properties and critical currents of MgB₂