Study of the second magnetization peak and the pinning behaviour in Ba(Fe _0.935 Co _0.065 ) ₂ As ₂ pnictide superconductor

Journal Article · Wed Nov 01 04:00:00 EDT 2017 · Superconductor Science and Technology

DOI:https://doi.org/10.1088/1361-6668/aa90b4· OSTI ID:1414684

Sundar, Shyam ^[1]; Mosqueira, J. ^[2]; Alvarenga, A. D. ^[3]; Sóñora, D. ^[2]; Sefat, A. S. ^[4]; Salem-Sugui, S. ^[1]

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1. Federal Univ. of Rio de Janeiro (Brazil). Inst. of Physics
2. Univ. of Santiago (Spain). Dept. of Particle Physics
3. National Inst. of Metrology Standardization and Industrial Quality, Rio de Janeiro (Brazil)
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Isothermal magnetic field dependence of magnetization and magnetic relaxation measurements were performed for the $$H\parallel {\rm{c}}$$ axis on a single crystal of Ba(Fe_0.935 Co_0.065)₂As₂ pnictide superconductor having T _c = 21.7 K. The second magnetization peak (SMP) for each isothermal M(H) was observed in a wide temperature range from T _c to the lowest temperature of measurement (2 K). The magnetic field dependence of relaxation rate R(H), showed a peak (H spt) between H on (onset of SMP in M(H)) and H p (peak field of SMP in M(H)), which is likely to be related to a vortex-lattice structural phase transition, as suggested in the literature for a similar sample. In addition, the magnetic relaxation measured for magnetic fields near H spt showed some noise, which might be the signature of the structural phase transition of the vortex lattice. Analysis of the magnetic relaxation data using Maley's criterion and the collective pinning theory suggested that the SMP in the sample was due to the collective (elastic) to plastic creep crossover, which was also accompanied by a rhombic to square vortex lattice phase transition. The analysis of the pinning force density suggested a single dominating pinning mechanism in the sample, which did not showing the usual $$\delta {l}$$ and $$\delta {T}_{{\rm{c}}}$$ nature of pinning. Furthermore, the critical current density (J _c), estimated using the Bean critical state model, was found to be 5 × 10⁵ A cm^{- 2} at 2 K in the zero magnetic field limit. Surprisingly, the maximum of the pinning force density was not responsible for the maximum value of the critical current density in the sample.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1414684
• Journal Information: Superconductor Science and Technology, Journal Name: Superconductor Science and Technology Journal Issue: 12 Vol. 30; ISSN 0953-2048
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
critical current density
iron-based superconductors
magnetic relaxation
second magnetization peak
single crystal
unconventional pinning