Competition of Superconductivity and Magnetism in MoSr2R1.5Ce0.5Cu2O10-d (R=Rare-earth, Mo-1222)

TL;DR

This study explores the interplay between superconductivity and magnetism in MoSr2R1.5Ce0.5Cu2O10-d compounds, revealing a competition between these states influenced by rare-earth elements and structural factors.

Contribution

It provides a comprehensive experimental analysis of how rare-earth substitution affects superconductivity and magnetic order in Mo-1222 compounds, introducing a simple model for the superconducting state.

Findings

Superconductivity vanishes when magnetic order appears in Mo-1222.

Light R ions are paramagnetic; middle R ions are superconducting at 18-23 K.

Heavy R ions exhibit antiferromagnetic order at 13-26 K.

Abstract

We have investigated the MoSr2R1.5Ce0.5Cu2O10-d (Mo-1222R, R=rare earth) system by several complementary experimental techniques. In contrast to the iso-structural RuSr2R1.5Ce0.5Cu2O10-d (Ru-1222) system, in which superconductivity (SC) in the CuO2 planes and weak-ferromagnetism in the Ru sub-lattice coexists, in Mo-1222, displays a competition between the two states, namely, SC vanishes when the magnetic order sets in. The contraction in the R elements leads to a change of the physical states. The light R ions (Pr and Nd) are paramagnetic down to 5 K, whereas the middle R ions (Sm and Eu) are SC at TC 18-23 K respectively. The SC charge carriers originate from the CuO2 planes, and annealing under oxygen pressures does not affect TC. A simple model for the SC state is proposed. For the heavy R elements Ho-Lu and Y, the pentavalent Mo layers are antiferromagnetically (AFM) ordered at TN ranging from 13-26 K. For R=Gd, the sample is not SC and exhibit two magnetic transitions at 11 and 184 K. Both the SC or AFM states depend strongly on the R/Ce ratio and for R/Ce=1, both states are suppressed.