1210.2309 (Yu. Talanov et al.)

Microwave absorption study of pinning regimes in $\bf
Ba(Fe_{1-x}Co_x)_2As_2$ single crystals    [PDF]

Yu. Talanov, N. Beisengulov, G. Kornilov, T. Shaposhnikova, E. Vavilova, C. Nacke, S. Wurmehl, N. Panarina, C. Hess, V. Kataev, B. Büchner

Magnetic field dependent modulated microwave absorption (MMWA) measurements have been carried out to investigate vortex pinning effects in single crystals of the iron-based high-Tc superconductor Ba(Fe_{1-x}Co_x)_2As_2 with three different cobalt doping levels of x = 0.07, 0.09, and 0.11. The dependence of the MMWA hysteresis loops on temperature, magnetic field, and Co-concentration have been measured and analyzed using a theoretical model of microwave absorption in superconductors. The analysis reveals that in an underdoped crystal (x = 0.07) the so called \dtc-pinning due to magnetically ordered regions defines the temperature dependence of the critical current density, while in the optimally doped (x = 0.09) and overdoped (x = 0.11) samples the pinning is governed by structural imperfections due to inhomogeneous distribution of cobalt dopant and has the so called \delta-l character.

View original: http://arxiv.org/abs/1210.2309