Effect of CuO Chains Ordering on the Opening of the Spin-Gap in YBa2Cu3O6+x

Abstract

The authors report on 63 Cu NMR relaxation measurements in YBa 2 Cu 3 O 6+x samples having similar T c's but a different structural ordering of the Cu(1)O chains. It is found that the gap in the spin excitations estimated from 63 Cu (2) nuclear spin-lattice relaxation rate 1/T1, varies from 110 K up to 190 K depending on the sample. This observation suggests that there is not a one to one relationship between the hole concentration and the amplitude of the spin-gap in the normal state of YBa 2 Cu 3 O 6+x. The sizeable variation in the gap, related to the different ordering of the Cu(1)O chains, is tentatively explained in the framework of a phase separation scenario where Cu(1)O chains act as pinning wells for the stripes.