We report on the systematic evolution of vortex pinning behavior in isovalent doped single crystals of BaFe2(As1-xPx)2. Proceeding from optimal doped to ovedoped samples, we find a clear transfor- mation of the magnetization hysteresis from a fishtai
l behavior to a distinct peak effect followed by a reversible magnetization and Bean Livingston surface barriers. Strong point pinning dominates the vortex behavior at low fields whereas weak collective pinning determines the behavior at higher fields. In addition to doping effects, we show that particle irradiation by energetic protons can tune vortex pinning in these materials.
We report the results of angle dependent resistivity of NdFeAsO$_{0.82}$F$_{0.18}$ single crystals in the superconducting state. By doing the scaling of resistivity within the frame of the anisotropic Ginzburg-Landau theory, it is found that the angl
e dependent resistivity measured under different magnetic fields at a certain temperature can be collapsed onto one curve. As a scaling parameter, the anisotropy $Gamma$ can be determined for different temperatures. It is found that $Gamma(T)$ increases slowly with decreasing temperature, varying from $Gamma simeq$ 5.48 at T=50 K to $Gamma simeq$ 6.24 at T=44 K. This temperature dependence can be understood within the picture of multi-band superconductivity.
