Study of the second magnetization peak and the pinning behaviour in Ba(Fe0.935Co0.065)2As2 pnictide superconductor. (1st November 2017)

• Record Type: Journal Article
• Authors: Sundar, Shyam; Mosqueira, J; Alvarenga, A D; Sóñora, D; Sefat, A S; Salem-Sugui, S
• Is Part Of: Superconductor science & technology. Volume 30:Number 12(2017:Dec.)
• Publication Date: 2017-11-01
• Subjects: iron-based superconductors -- single crystal -- second magnetization peak -- magnetic relaxation -- critical current density -- unconventional pinning; Superconductivity -- Periodicals; Superconductors -- Periodicals; 537.623
• DOI: 10.1088/1361-6668/aa90b4
• Languages: English
• ISSNs: 0953-2048

Abstract

Abstract: Isothermal magnetic field dependence of magnetization and magnetic relaxation measurements were performed for the H ∥ c axis on a single crystal of Ba(Fe0.935 Co0.065 )2 As2 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. Analysis of the pinning force density suggested a single dominating pinning mechanism in the sample, which did not showing the usual δ l and δ T c nature of pinning. The critical current density ( J c ), estimated using the Bean critical state model, was found to be 5 × 10 5 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.