Cu-NQR study on single crystals Sr14-xCaxCu24O41 with x = 0-11.5

Abstract

Cu-nuclear quadrupole resonance (NQR) measurements have been performed on single crystals Sr 14-x Ca x Cu 24 O 41 (Ca x ) with x =0-11.5, in order to clarify the relation between the magnetic order around x =11.5 and local environments at the Cu sites upon x. Cu-NQR frequency ν Q for the ladders at 4.2 K increases linearly with increasing x, whereas ν Q for the nonmagnetic Zhang-Rice (ZR) sites in the chains does not. Detailed site assignment of the spectra, which are different from those in the previous paper, is presented.