Mössbauer studies of YBa2(Cu1−x Fe x )3O7−d annealed in an inert atmosphere

YBa2(Cu1−xFe x )3O7−d annealed in an Ar atmosphere, then reoxygenated at various temperatures, has been studied by Mossbauer spectroscopy at 300 K and low temperature with and without an applied field of 5.5 T. The results are interpreted as being due to Fe clustering remaining in the chains rather than a significant transfer to the planes.