Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 15: Superconductivity: Poster Session

TT 15.7: Poster

Dienstag, 26. Februar 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 T_c and T_m 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 T_c and an increase of T_m. 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 T_c and T_m. This is compatible with the results of experiments where Ru is partially substituted by Cu.