Étude par résonance quadrupolaire nucléaire de la rétention de carbone dans l'YBa2Cu3Oy≈7

Abstract

We present a Nuclear Quadrupole Resonance (NQR) study of Cu(2) (planes) and Cu(1) (chains) sites in two YBa 2 Cu 3 O y ≈7 powder samples with carbon concentration equal to 500 ppm and 3000 ppm, and in a free-carbon sample. By comparison with standard spectra in YBa 2 Cu 3 O y , we show that a new NQR line appears at 30.90 MHz, the intensity of which is strongly correlated with the amount of carbon in the sample. Moreover, according to the spin-lattice relaxation rate 1/ T 1 measurements at different frequencies of the spectrum, we attribute this anomalous line to the formation of clusters in which the superconductivity is destroyed by the presence of carbonate groups, which substitute preferentially for copper chain site. Those results are in good agreement with those of Wang et al. [1], obtained by high resolution electron microscopy.