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Paul C. Canfield - One of the best experts on this subject based on the ideXlab platform.

  • Variation of transition temperatures and residual Resistivity Ratio in vapor-grown FeSe
    Physical Review B, 2016
    Co-Authors: Anna E. Böhmer, Valentin Taufour, Warren E. Straszheim, T. Wolf, Paul C. Canfield
    Abstract:

    The study of the iron-based superconductor FeSe has blossomed with the availability of high-quality single crystals, obtained through flux/vapor-transport growth techniques below the structural transformation temperature of its tetragonal phase, $T\ensuremath{\approx}450{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$. Here, we report on the variation of sample morphology and properties due to small modifications in the growth conditions. A considerable variation of the superconducting transition temperature ${T}_{\mathrm{c}}$, from 8.8 K to 3 K, which cannot be correlated with the sample composition, is observed. Instead, we point out a clear correlation between ${T}_{\mathrm{c}}$ and disorder, as measured by the residual Resistivity Ratio. Notably, the tetragonal-to-orthorhombic structural transition is also found to be quite strongly disorder dependent $({T}_{\mathrm{s}}\ensuremath{\approx}72--90\phantom{\rule{4pt}{0ex}}\text{K})$ and linearly correlated with ${T}_{\mathrm{c}}$.

  • Low temperature magnetic transitions of single crystal HoBi
    Solid State Communications, 2013
    Co-Authors: A. Fente, Hermann Suderow, Sebastian Vieira, Norbert M. Nemes, Mar García-hernández, Sergey L. Bud’ko, Paul C. Canfield
    Abstract:

    We present Resistivity, specific heat and magnetization measurements in high quality single crystals of HoBi, with a residual Resistivity Ratio of 126. We find, from the temperature and field dependence of the magnetization, an antiferromagnetic transition at 5.7 K, which evolves, under magnetic fields, into a series of up to five metamagnetic phases.

Yoshichika Ōnuki - One of the best experts on this subject based on the ideXlab platform.

Rikio Settai - One of the best experts on this subject based on the ideXlab platform.

  • High-quality single crystal growth of UGe2 and URhGe
    Journal of Magnetism and Magnetic Materials, 2004
    Co-Authors: Etsuji Yamamoto, Yoshinori Haga, Tatsuma D. Matsuda, Shugo Ikeda, Yoshihiko Inada, Rikio Settai, Yoshichika Ōnuki
    Abstract:

    Abstract We searched for an experimental condition of crystal growth for a ferromagnetic superconductors of UGe 2 and URhGe. Samples were prepared for both polycrystalline and single crystals, which were arc-melted and grown by the Czochralski-pulling method in a tetra-arc furnace, respectively. Annealing is an important process to enhance sample-quality, namely the residual Resistivity Ratio. We tried to anneal the samples under various temperatures, which were wrapped by the Ta-foil and vacuum-sealed in the quartz ample, together with the solid state electrotransport method in ultra-high vacuum. The highest residual Resistivity Ratio was 900 for UGe 2 and 41 for URhGe.

  • High-quality single-crystal growth and a change of the electronic states under pressure in CeRh2Si2
    Journal of Magnetism and Magnetic Materials, 2001
    Co-Authors: Shingo Araki, Rikio Settai, Tatsuya Kobayashi, Yoshichika Ōnuki
    Abstract:

    Abstract We succeeded in growing a high-quality single crystal of CeRh 2 Si 2 with a residual Resistivity Ratio of 110. Under a pressure of 1.1 GPa, superconductivity is found below T c =0.38 K, where a Neel temperature of T N =36 K is suppressed down to almost zero.

  • Electronic States of the Antiferromagnet UGa3
    Journal of the Physical Society of Japan, 2001
    Co-Authors: Dai Aoki, Etsuji Yamamoto, Yoshinori Haga, Yoshihiko Inada, Rikio Settai, Norihito Suzuki, K. Miyake, Kiyohiro Sugiyama, Yoshichika Onuki, Tetsutaro Inoue
    Abstract:

    We have grown a single crystal with the residual Resistivity Ratio of 81, and studied its electronic properties of the cubic antiferromagnetic compound UGa 3 . From the transverse magnetoresistance...

Shriram Ramanathan - One of the best experts on this subject based on the ideXlab platform.

  • Stability of electrical switching properties in vanadium dioxide thin films under multiple thermal cycles across the phase transition boundary
    Journal of Applied Physics, 2008
    Co-Authors: Changhyun Ko, Shriram Ramanathan
    Abstract:

    The influence of successive thermally induced metal-insulator transition (MIT) on electrical transition characteristics in high quality vanadium dioxide (VO2) thin films synthesized by reactive sputtering was investigated in conjunction with structural studies. We show that the transition quality of VO2 thin films was largely unaffected up to ∼100 heating-cooling cycles with respect to hysteresis width, Resistivity Ratio, and MIT onset temperature. The hysteresis width decreased by ∼3% along with an enhancement in film texture, while no reduction in Resistivity Ratio or MIT temperature was observed, implying that the stoichiometry of overall VO2 thin film did not degrade under multiple thermally induced transitions. The results are of potential relevance to solid state sensing elements utilizing vanadium oxide.

N N Martovetsky - One of the best experts on this subject based on the ideXlab platform.

  • Influence of heat treatment excursion on critical current and residual Resistivity Ratio of ITER Nb 3 Sn strands
    Superconductor Science and Technology, 2017
    Co-Authors: D R Mcguire, S Hill, R Niu, K Chan, N N Martovetsky
    Abstract:

    Heat treatment is critically important to the performance of Nb3Sn superconducting strands. For very large Nb3Sn magnet coils, such as the International Thermonuclear Experimental Reactor (ITER) Central Solenoid (CS) coils, heat treatment carries risk of temperature and time excursion, which may result in performance degradation. Therefore, it is prudent to study the effect of possible excursion on Nb3Sn performance. In this study, Nb3Sn strands used for ITER CS coils are heat treated at different temperatures for different times. Their critical current, residual resistance Ratio and hysteresis losses are measured. It is found that in the range we studied, critical current and hysteresis losses do not change significantly. Residual resistance Ratio, however, decreases with increasing heat treatment temperature and time. This is attributed to the diffusion of metallic elements from the plated Cr layer to the copper stabilizer. Based on a model of metallic elements diffusion, a numerical code is developed to predict residual resistance Ratio as a function of heat treatment temperature and time.

  • influence of heat treatment excursion on critical current and residual Resistivity Ratio of iter nb3sn strands
    arXiv: Superconductivity, 2017
    Co-Authors: D R Mcguire, S Hill, R Niu, K Chan, N N Martovetsky
    Abstract:

    Heat treatment is critically important to the performance of Nb3Sn superconducting strands. For very large Nb3Sn magnet coils, such as the International Thermonuclear Experimental Reactor (ITER) Central Solenoid (CS) coils, heat treatment carries risk of temperature and time excursion, which may result in performance degradation. Therefore, it is prudent to study the effect of possible excursion on Nb3Sn performance. In this study, Nb3Sn strands used for ITER CS coils are heat treated at different temperatures for different times. Their critical current, residual resistance Ratio and hysteresis losses are measured. It is found that in the range we studied, critical current and hysteresis losses do not change significantly. Residual resistance Ratio, however, decreases with increasing heat treatment temperature and time. This is attributed to the diffusion of metallic elements from the plated Cr layer to the copper stabilizer. Based on a model of metallic elements diffusion, a numerical code is developed to predict residual resistance Ratio as a function of heat treatment temperature and time.