SYSTEMATIC MOSSBAUER STUDY OF YBA2CU3-XFEXO-DELTA AND PRBA2CU3-XFEXO DELTA AS A FUNCTION OF TEMPERATURE

Abstract

We study the similitudes and differences between YBa2Cu3-xFexO-delta and PrBa2Cu3-xFexO-delta systems, using Mossbauer spectroscopy. Both systems, with z = 0.04, were studied at several temperatures. The spectra of YBa2Cu3-xFeO-delta showed four asymmetric quadrupole doublets with apparently different line widths, which were fitted with four symmetric superimposed quadrupole doublets with the same line width, but assuming a small (approximately 4-6 kOe) residual magnetic field in the Fe sites, which are mainly the Cu(1) sites of the 1-2-3 structure. On the other hand, the PrBa2Cu3-xFeO-delta spectra showed only three asymmetric quadrupole doublets which can be fitted with three superimposed symmetric doublets and a residual magnetic field. In this case, the Fe atoms also occupy the Cu(l) sites of the 1-2-3 structure. The temperature variations of the Mossbauer spectra and their parameters seem to indicate that, in the Pr-system, a structural change takes place between 12 K and 40 K.