A Precise Measurement of the Oxygen Isotope Effect on the N\'{e}el temperature in Cuprates

TL;DR

This study precisely measures the oxygen isotope effect on the antiferromagnetic transition temperature in cuprates, revealing no significant isotope effect and suggesting isotope substitution influences charge carrier density.

Contribution

It introduces a novel compound enabling accurate T_N measurements across doping levels, overcoming previous sensitivity issues, and provides the first precise data showing no isotope effect on T_N.

Findings

No isotope effect on T_N detected with high accuracy

T_N is independent of oxygen doping in the studied compound

Isotope substitution may affect charge carrier density

Abstract

A limiting factor in the ability to interpret isotope effect measurements in cuprates is the absence of sufficiently accurate data for the whole phase diagram; there is precise data for Tc, but not for the antiferromagnetic transition temperature T_N. Extreme sensitivity of T_N to small changes in the amount of oxygen in the sample is the major problem. This problem is solved here by using the novel compound (Ca 0.1 La 0.9)(Ba 1.65 La 0.35)Cu 3 O y for which there is a region where T_N is independent of oxygen doping. Meticulous measurements of T_N for samples with oxygen 16 and oxygen 18 find the absence of an oxygen isotope effect on T_N with unprecedented accuracy. A possible interpretation of our finding and existing data is that isotope substitution affects the normal state charge carrier density.