Angular dependence of pinning potential, upper critical field, and irreversibility field in underdoped BaFe1.9Co0.1As2 single crystal

Underdoped BaFe1.9Co0.1As2 single crystal was studied by angular dependence of

magneto-transport at fields up to 13 T over a wide range of temperature. Our results show that

pinning potential, Uo, decreases slightly for h45 and remains constant for h45, while

the upper critical field, Hc2, and the irreversibility field, Hirr, increase with h. According to

anisotropic Ginzburg-Landau theory, the anisotropy was determined by scaling the resistivity

under different magnetic fields below the superconducting critical temperature, Tc. Anisotropy,

C, in the underdoped crystal is found to be temperature dependent and decreases from

2.1 to 1.8 for as T is reduced from 17 to 12.5 K.