Magneto-transport Properties and Thermally Activated Flux Flow in Ba(Fe0.91Co0.09)(2)As-2 Superconductor

作者：Nikolo M^*; Shi X; Choi E S; Jiang J; Weiss J D; Hellstrom E E

来源：Journal of Superconductivity and Novel Magnetism, 2014, 27(10): 2231-2239.

DOI：10.1007/s10948-014-2587-z

• Superconductors
• Pnictides
• Magnetic measurements
• Thermally activated flux flow
• Pinning energies
• Upper critical magnetic field
• Phase diagram
• Magneto-resistivity
• Ac susceptibility
• Ac losses

Thermally assisted flux flow (TAFF) based on magneto-resistivity and ac susceptibility measurements is studied in a Ba(Fe0(91Co0(09)(2)As-2(T-c = 25.3 K) sample in magnetic fields up to 18 T. In addition to the upper critical field mu H-0(c2) and the coherence length xi(0), the flux flow activation energy U T H has also been determined. The resistive transition width is proportional to mu H-0, in contrast to Tinkham%26apos;s theoretical prediction. By applying Fisher%26apos;s model, the glass melting transition temperature T-g, which occurs in the upper TAFF state and not in the zero resistivity vortex solid regime, is calculated. The onset of TAFF temperature and the crossover temperature T-x from TAFF to flux flow are determined. By contrasting the ac susceptibility data with the resistivity data, considerable flux penetration appears even in the zero resistivity state, in addition to ac losses. The H-T phase diagram is drawn and shows weak pinning regime as the field approaches mu H-0(c2), and the strength of the weak pinning decreases to 0 with increasing magnetic field from 0 to 18 T.

• 出版日期2014-10