The interplay of charge order and magnetism in Sr14Cu24O41 and Sr13LaCu24O41

We examined the doping dependence of the charge order in the spin chains of Sr14Cu24O41 and Sr13LaCu24O41 by 63Cu-NMR. In Sr14Cu24O41we verified the existence of two distinct Zhang–Rice copper sites on the chains with a dimer local susceptibility in agreement with the macroscopic susceptibility. In Sr13LaCu24O41 one broad line associated with a Zhang–Rice site is observed. In contrast to expectations motivated by the charge order model this signal also exhibits a thermally activated local susceptibility. [Copyright &y& Elsevier]