Berlin 2008 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 15: Superconductivity: Poster Session
TT 15.7: Poster
Tuesday, February 26, 2008, 14:00–18:00, Poster B
Effect of variable Ru content on superconducting and magnetic properites of RuSr2GdCu2O8 — •Manuel Kempf, Eugenio Casini, and Hans F. Braun — Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth
We have investigated the effect of a variation of the Ru content in RuSr2GdCu2O8 (RuGd1212) on sample properties as for example shifts of the superconducting and magnetic transition temperatures Tc and Tm and the presence of phases in equilibrium with RuGd1212. The procedure of sample preparation can strongly affect the magnetic and superconducting properties of RuGd1212. Due to the relatively high volatility of the Ru-oxides at temperatures around 1000∘C, a Ru loss can arise during calcination of the starting materials, the preparation of the Sr2RuGdO6 precursor and the final sintering process of RuGd1212.
The starting composition for our RuGd1212 was a mixture of CuO and Sr2RuGdO6 in the stoichiometric ratio 2:1. Samples were sintered in an O2/Ru-oxide gas flow with variable Ru content. An increase of the Ru concentration in the gas mixture leads to a decrease of Tc and an increase of Tm. In sample areas exposed to the gas flow, additional phases coexisting with RuGd1212 were observed at higher Ru-oxide partial pressure. Thus, sintering of RuGd1212 in O2/Ru-oxide gas flow with variable partial pressure of Ru-oxide controls the loss or increase of Ru in RuGd1212. The different Ru contents in RuGd1212 result in changes of Tc and Tm. This is compatible with the results of experiments where Ru is partially substituted by Cu.