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Title: Upper critical and irreversibility fields in Ni- and Co- doped pnictide bulk superconductors

Abstract

Comprehensive study of upper critical and irreversibility magnetic fields in Ba(Fe 0.95Ni 0.05) 2As 2 (large grain and small grain samples or Ni5(SG), Ni5(LG)), Ba(Fe 0.94Ni 0.06) 2As 2 (Ni6), Ba(Fe 0.92Co 0.08) 2As 2 (Co8), and Ba(Fe 0.92Co 0.09) 2As 2 (Co9) polycrystalline bulk pnictide superconductors was made in pulsed fields of up to 65 T.

Authors:
 [1];  [2];  [1];  [3];  [3];  [3]
  1. Saint Louis Univ., St. Louis, MO (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Florida State Univ., Tallahassee, FL (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1343724
Report Number(s):
LA-UR-17-21120
DOE Contract Number:
AC52-06NA25396
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; High Magnetic Field Science

Citation Formats

Nikolo, Martin, Singleton, John, Solenov, Dmitry, Jiang, Jianyi, Weiss, Jeremy, and Hellstorm, Eric. Upper critical and irreversibility fields in Ni- and Co- doped pnictide bulk superconductors. United States: N. p., 2017. Web. doi:10.2172/1343724.
Nikolo, Martin, Singleton, John, Solenov, Dmitry, Jiang, Jianyi, Weiss, Jeremy, & Hellstorm, Eric. Upper critical and irreversibility fields in Ni- and Co- doped pnictide bulk superconductors. United States. doi:10.2172/1343724.
Nikolo, Martin, Singleton, John, Solenov, Dmitry, Jiang, Jianyi, Weiss, Jeremy, and Hellstorm, Eric. Mon . "Upper critical and irreversibility fields in Ni- and Co- doped pnictide bulk superconductors". United States. doi:10.2172/1343724. https://www.osti.gov/servlets/purl/1343724.
@article{osti_1343724,
title = {Upper critical and irreversibility fields in Ni- and Co- doped pnictide bulk superconductors},
author = {Nikolo, Martin and Singleton, John and Solenov, Dmitry and Jiang, Jianyi and Weiss, Jeremy and Hellstorm, Eric},
abstractNote = {Comprehensive study of upper critical and irreversibility magnetic fields in Ba(Fe0.95Ni0.05)2As2 (large grain and small grain samples or Ni5(SG), Ni5(LG)), Ba(Fe0.94Ni0.06)2As2 (Ni6), Ba(Fe0.92Co0.08)2As2 (Co8), and Ba(Fe0.92Co0.09)2As2 (Co9) polycrystalline bulk pnictide superconductors was made in pulsed fields of up to 65 T.},
doi = {10.2172/1343724},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Feb 13 00:00:00 EST 2017},
month = {Mon Feb 13 00:00:00 EST 2017}
}

Technical Report:

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  • The de-pinning or irreversibility lines were determined by ac susceptibility, magnetization, radio-frequency proximity detector oscillator (PDO), and resistivity methods in Ba(Fe 0.92Co 0.08) 2As 2 ( T c = 23.2 K), Ba(Fe 0.95Ni 0.05) 2As 2 ( T c = 20.4 K), and Ba(Fe 0.94Ni 0.06) 2As 2 ( T c = 18.5 K) bulk superconductors in ac, dc, and pulsed magnetic fields up to 65 T. A new method of extracting the irreversibility fields from the radio-frequency proximity detector oscillator induction technique is described. Wide temperature broadening of the irreversibility lines, for any given combination of ac and dcmore » fields, is dependent on the time frame of measurement. Increasing the magnetic field sweep rate (dH/dt) shifts the irreversibility lines to higher temperatures up to about dH/d t = 40,000 Oe/s; for higher dH/dt, there is little impact on the irreversibility line. There is an excellent data match between the irreversibility fields obtained from magnetization hysteresis loops, PDO, and ac susceptibility measurements, but not from resistivity measurements in these materials. Lower critical field vs. temperature phase diagrams are measured. Their very low values near 0 T indicate that these materials are in mixed state in nonzero magnetic fields, and yet the strength of the vortex pinning enables very high irreversibility fields, as high as 51 T at 1.5 K for the Ba(Fe 0.92Co 0.08) 2As 2 polycrystalline sample, showing a promise for liquid helium temperature applications.« less
  • The electrical resistivity of (Y{sub 1-x}Pr{sub x})Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} and YBa{sub 2}(Cu{sub 1-x}Zn{sub x})O{sub 7-{delta}} thin films and (Y{sub 1-x}Tb{sub x})Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films and single crystals has been measured as a function of 0 {le} x {le} x{sub crit}, 2K {le} T {le} 300K and OT {le} H {le} 20T. The samples were oriented with c-axis parallel to applied fields. Upper critical field H{sub c2} and irreversibility field H{sub irr} values have been determined from these measurements. Increased Tb doping appears to shift H{sub irr} to higher temperatures. This coupled with observed twin peaks in magnetizationmore » measurements reflects an enhancement of flux pinning. Unlike Tb which does not appear to alter T{sub c}, Pr and Zn doping of this system tends to depress both T{sub c} and the slope of the mean field normal phase-mixed phase boundary line (dH{sub c2}/dT).« less
  • The maximum supercurrent that can be carried in an applied perpendicular magnetic field by a superconducting-normal-metal-superconducting (SNS) junction consisting of a square normal-metal layer sandwiched between two crossed perpendicular superconducting strips is investigated theoretically. For weak applied fields, the critical current is suppressed reversibly, as induced Meissner screening currents flow into the SNS sandwich and generate a spatially varying magnetic field largely parallel to the junction, thereby altering the local phase difference. For stronger applied fields, the critical current is changed irreversibly as vortices enter and become pinned in the junction. When the pinned vortices in the two superconductors aremore » misaligned, the local magnetic field, which flows mostly parallel to the junction in carrying magnetic flux from one vortex to the other, strongly alters the phase difference across the junction near the two vortices. The theory predicts complex patterns of the supercurrent density, which should be directly observable using laser or electron-beam scanning techniques. Eilenberger's quasi-classical formulation of superconductivity is used to derive an equation for the upper critical field of a multilayered SN system in a perpendicular magnetic field. The alternating layers are coupled via the proximity effect and are in the dirty limit. Comparison with experimental data for Nb/Cu multilayers shows good agreement only if the mean free paths are substantially smaller than those obtained from longitudinal resistivity measurements. One feature of this theory is the presence of positive curvature in the upper critical field near the critical temperature.« less
  • Controlled chemical doping of magnesium diboride (MgB2) has been shown to substantially improve its superconducting properties to the levels required for high field magnets, but the doping is difficult to accomplish through the usual route of solid state reaction and diffusion. Further, superconducting cables of MgB2 are difficult to fabricate because of the friable nature of the material. In this Phase I STTR project, doped and undoped boron fibers were made by chemical vapor deposition (CVD). Several >100m long batches of doped and undoped fiber were made by CVD codeposition of boron plus dopants. Bundles of these fibers infiltrated withmore » liquid magnesium and subsequently converted to MgB2 to form Mg-MgB2 metal matrix composites. In a parallel path, doped boron nano-sized powder was produced by a plasma synthesis technique, reacted with magnesium to produce doped MgB2 superconducting ceramic bodies. The doped powder was also fabricated into superconducting wires several meters long. The doped boron fibers and powders made in this program were fabricated into fiber-metal composites and powder-metal composites by a liquid metal infiltration technique. The kinetics of the reaction between boron fiber and magnesium metal was investigated in fiber-metal composites. It was found that the presence of dopants had significantly slowed the reaction between magnesium and boron. The superconducting properties were measured for MgB2 fibers and MgB2 powders made by liquid metal infiltration. Properties of MgB2 products (Jc, Hc2) from Phase I are among the highest reported to date for MgB2 bulk superconductors. Chemically doped MgB2 superconducting magnets can perform at least as well as NbTi and NbSn3 in high magnetic fields and still offer an improvement over the latter two in terms of operating temperature. These characteristics make doped MgB2 an effective material for high magnetic field applications, such as magnetic confined fusion, and medical MRI devices. Developing fusion as an energy source will dramatically reduce energy costs, global warming, and radioactive waste. Cheaper and more efficient medical MRI devices could lower examination costs, find potential health problems earlier, and thus also benefit society as a whole. Other potential commercial applications for this material are devices for the generation and storage of electrical power, thus lowering the cost of delivered electricity.« less