Preparation of superconducting RuGd-1222 single crystals by partial melting

Abstract

Growth of single crystals of RuGd-1222 ((Gd,Ce)2Sr2RuCu2O10−δ) remains a major challenge, and previous studies have indicated that epitaxial thin films of these compounds exhibit deteriorated superconductivity. We have been working toward the synthesis of RuGd-1222 single crystals using the self-flux and partial melting techniques. In this paper, we report on the synthesis of RuGd-1222 single-crystal lumps by partial melting. The maximum size of a single crystal was approximately 80 μm in length, which is almost the same as that of our previous studies by self-flux method. Although these samples contained some impurity phases, the predominant phase was confirmed to be RuGd-1222. Furthermore, following optimization of the synthetic conditions, superconductivity with an onset transition temperature (Tc-onset) of 27 K was observed for a RuGd-1222 single-crystal lump prepared by partial melting. Local decomposition from RuGd-1222 plate-like crystals to RuGd-1212 single crystals was observed after prolonged sintering. The synthesis of single crystals of ruthenocuprates by partial melting is expected to contribute to an improved understanding of this class of magnetosuperconductors.