Scanning Tunneling Microscopy of Fe Impurities in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+d}$

We utilize scanning tunneling microscopy measurements to probe the effects of intentionally doped magnetic Fe impurities in the high-temperature superconductor Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+d}$. Our spectroscopy measurements indicate an absence of particle-hole symmetry in impurity affected regions. In addition, we find evidence that the Fe impurities which substitute for Cu atoms in the CuO$_{2}$ plane are shifted from their expected locations. Both of these findings are in contrast to previous STM measurements on magnetic Ni impurities in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+d}$ which find spectra which are overall particle-hole symmetric and centered at Cu sites.[1] Interpretations of our measurements may help us understand on a local scale why introduced Fe impurities are more detrimental to superconductivity than Ni impurities as determined by bulk measurements.[2] [1] E.W. Hudson et al., Nature 411, 920 -- 924 (2001). [2] T.D. Hien et al., J. Magn. Magn. Mater. 262, 508 -- 513 (2003).