Doping and Irradiation Controlled Vortex Pinning Behavior in   BaFe2(As1-xPx)2 Single Crystals
  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 fishtail 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. 
L. Fang, Y. Jia, J. A. Schlueter, A. Kayani, Z. L. Xiao, H. Claus, U.   Welp, A. E. Koshelev, G. W. Crabtree and W.-K. Kwok
cond-mat.supr-con