Magnetism and superconductivity in Ru(1-x)Sr2RECu(2+x)O(8-d) (RE=Gd, Eu) and RuSr2Gd(1-y)Ce(y)Cu2O8 compounds

TL;DR

This study explores the synthesis, magnetic, and superconducting properties of Ru-based ruthenocuprates with variable composition, revealing how doping and oxygen content influence their transition temperatures and magnetic behavior, and proposing a phase diagram for these materials.

Contribution

The paper introduces new superconducting ruthenocuprate compositions with tunable Tc and magnetic properties, and proposes a phase diagram linking doping levels to their physical characteristics.

Findings

Tc reaches up to 72 K with Cu-Ru substitution.

Magnetic transitions observed at low temperatures (2-14 K).

Doping and oxygen content effectively tune superconductivity and magnetism.

Abstract

We discuss the properties of new superconducting compositions of Ru(1-x)Sr2RECu(2+x)O(8-d) (RE=Gd, Eu) ruthenocuprates that were synthesized at 600 atm. of oxygen at 1080 C. By changing ratio between the Ru and Cu, the temperature of superconducting transition (Tc) raises up to Tc max=72 K for x=0.3, 0.4. The hole doping achieved along the series increases with Cu->Ru substitution. For x different than x=0, Tc can be subsequently tuned between Tc max and 0 K by changing oxygen content in the compounds. The magnetic characteristics of the RE=Gd and Eu based compounds are interpreted as indicative of constrained dimensionality of the superconducting phase. Muon spin rotation experiments reveal the presence of the magnetic transitions at low temperatures (Tm=14-2 K for x=0.1-0.4) that can originate in the response of Ru/Cu sublattices. RuSr2Gd(1-y)Ce(1-y)Cu2O8 (0<y<0.1) compounds show the simultaneous increase of TN and decrease of Tc with y. The effect should be explained by the electron doping that occurs with Ce->Gd substitution. Properties of these two series allow us to propose phase diagram for 1212-type ruthenocuprates that links their properties to the hole doping achieved in the systems. Non-superconducting single-phase RuSr2GdCu2O8 and RuSr2EuCu2O8 are reported and discussed in the context of the properties of substituted compounds.