Pristupačnost
We present 63Cu Nuclear Magnetic Resonance (NMR) measurements on undoped SrCuO2 and Ca-doped Sr0:9Ca0:1CuO2 single crystals. The crystal structure contains one-dimensional CuO2 double chains that are magnetically decoupled due to frustration. The system orders magnetically only below _2 K. Nevertheless, the Cu NMR spectra broaden already at temperatures below 100K and show an anomalous two peak structure at low temperatures, which are still far above the magnetic ordering temperature. For the Ca-doped sample, this broadening is reduced. The reason for this unusual broadening is not known, but a similar broadening has been reported for the single chain compound Sr2CuO3.