Magnetic properties of single-crystal Y-Ba-Cu-O containing Fe

A single-crystal of YBa2Cu2.85Fe0.15O 7 was found to be tetragonal over the temperature range 10-300 K. The iron obeyed a Curie-Weiss law attributed to divalent Fe and showed a negative intercept indicating antiferromagnetic exchange. The presence of Fe degraded the superconducting properties such that critical currents are only 10%-20% of that in the best pure YBa2Cu3O7-δ crystals without Fe and the superconducting transition temperature has decreased from 90 to 60 K.