A Precise Measurement of the Oxygen Isotope Effect on the N\'eel temperature in Cuprates
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 TN. Extreme sensitivity of TN 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 TN is independent of oxygen doping. Meticulous measurements of TN for samples with oxygen 16 and oxygen 18 find the absence of an oxygen isotope effect on TN with unprecedented accuracy. A possible interpretation of our finding and existing data is that isotope substitution affects the normal state charge carrier density.