Oxygen content and valence of Ru in RuSr2(Gd0.75Ce0.25)(2)Cu2O10-delta (Ru-1222) magnetosuperconductor
Journal
Journal of Low Temperature Physics
Journal Volume
131
Journal Issue
5-6
Pages
1211-1216
Date Issued
2003
Author(s)
Abstract
The valence of Ru was analyzed for two RuSr2 (Gd0.75 Ce0.25)2 Cu2 O10-δ samples with different oxygen contents by Ru LIII-edge x-ray absorption near-edge structure (XANES) spectroscopy. For the sample as-synthesized in 1 atm O2 the DC magnetization data measured in an applied field of 5 Oe showed a clear branching of the zero-field-cooled (ZFC) and field-cooled (FC) curves around 140 K, and up-turn for both around 100 K and a cusp at 85 K and a diamagnetic transition around 20 K in the ZFC part. A further confirmation for the superconductivity at 23 K was obtained from a resistance us. temperature measurement. Annealing the as-synthesized sample in 100-atm O2 atmosphere at 420 °C increased the diamagnetic transition temperature from 20 K to 40 K. According to a thermogravimetric analysis, the oxygen content increased accordingly by ca. 0.1 oxygen atoms per formula unit. Quantitative analysis of the XANES spectra using Sr2RuO4 (RuIV) and Sr2 GdRuO6 (RuV) as reference materials revealed a valence value of +4.74 and +4.81 for Ru in the as-synthesized and the 100-atm O2-annealed sample, respectively. The obtained result suggests that the valence of Ru in Ru-1222 is affected by the change in oxygen content.
Type
journal article