Anisotropy and Vortex Pinning of Heavy Ion irradiated SmFeAsO$_{0.8}$F$_{0.15}$ and BaFe$_{2}$(As$_{1-x}$P$_{x})_{2}$ Crystals
ORAL
Abstract
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.
*Work supported by the US DoE-BES funded Energy Frontier Research Center (LF, CC, YJ, GWC), and by Department of Energy, Office of Science, Office of Basic Energy Sciences (WKK, UW, AEK, SFZ), under Contract No. DE-AC02-06CH11357
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