Anisotropy and Vortex Pinning of Heavy Ion irradiated SmFeAsO$_{0.8}$F$_{0.15}$ and BaFe$_{2}$(As$_{1-x}$P$_{x})_{2}$ Crystals

We report specific heat and magnetization measurements on SmFeAsO$_{0.8}$F$_{0.15}$ and BaFe$_{2}$(As$_{1-x}$P$_{x})_{2}$ single crystals irradiated with high energy heavy ions of 1.4GeV Pb to dose matching fields up to 4 Tesla. We find a nearly one half reduction in the superconducting anisotropy and doubling of the irreversibility field in SmFeAsO$_{0.8}$F$_{0.15 }$after irradiation and virtually no change in the zero-field superconducting transition temperature. In both SmFeAsO$_{0.8}$F$_{0.15}$ and BaFe$_{2}$(As$_{1-x}$P$_{x})_{2}$ crystals, we find a substantial increase in the critical current determined from SQUID and micro-Hall probe magnetization measurements. Pinning force analysis on proton and heavy ion irradiated pristine overdoped BaFe$_{2}$(As$_{1-x}$P$_{x})_{2}$ crystals indicates presence of induced $\Delta $T$_{c}$-type pinning defects in these samples.