Relevance of magnetism to cuprate superconductivity: Lanthanides versus charge-compensated cuprates

TL;DR

This study investigates the relationship between magnetism and superconductivity in cuprates, comparing lanthanide-based and charge-compensated series, revealing that magnetic coupling varies weakly in one series but correlates with superconducting temperature in the other.

Contribution

It provides new insights into how magnetic interactions relate to superconductivity across different cuprate families, highlighting the contrasting behaviors of REBa₂Cu₃O_y and CLBLCO.

Findings

Normalized magnetic order parameter is identical across RE123 compounds (except Gd123).

Weak variation of superexchange interaction J in RE123 limits testing its relation to Tc.

Positive correlation between Tc^{max} and T_N^{max} observed in CLBLCO.

Abstract

We address what seemed to be a contradiction between the lanthanide series REBa$_2$Cu$_3$O$_y$ (RE123) and the charge-compensated series (Ca$_{x}$La$_{1-x}$)(Ba$_{1.75-x}$La$_{0.25+x} $)Cu$_{3}$O$_{y}$ (CLBLCO) regarding the superexchange ($J$) dependence of the maximum superconductivity (SC) critical temperature $T_c^{max}(J)$; RE and $x$ are implicit variables. This is done by measuring the N\'{e}el temperature and the temperature dependence of the magnetic order parameter for RE=Nd, Sm, Eu, Gd, Dy, Yb, Y, and for Y(BaSr)Cu$_3$O$_y$, at various very light dopings. The doping is determined by thermopower, and the magnetic properties by muon spin rotation. We find that the normalized-temperature dependence of the order parameter is identical for all RE123 in the undoped limit (with the exception of Gd123) implying identical out-of-plane magnetic coupling. The extrapolation of $T_N$ to zero doping suggests that, despite the variations in ionic radii, $J$ varies too weakly in this system to test the relation between SC and magnetism. This stands in contrast to CLBLCO where both $T_c^{max}$ and $T_N^{max}$ vary considerably in the undoped limit, and a positive correlation between the two quantities was observed.