Nuclear quadrupole resonance of Cu in hydrogenated YBa2Cu3O7

The Cu65 and Cu63 NQR lines were obtained at a temperature of 4.2 K for samples of HxYBa2Cu3O7, where x=0.021, 0.058, 0.21, 0.60, and 1.00. New peaks appear upon the introduction of hydrogen. The amplitudes of the various peaks rise and fall but do not change their positions continuously as x is varied. The positions of the peaks are attributed to changes in the valency of the Cu atoms, which are thus seen to change in a discontinuous manner as x changes. The positions of the new lines that appear are the same as those obtained when oxygen is removed. The disappearance of the Cu63 31.5 MHz line for the nonsuperconducting material having x=1.00, is attributed to antiferromagnetic order. The results confirm our previous assertion that adding hydrogen to YBa2Cu3O7 changes many of the attributes of the material in a manner similar to removing oxygen. Possible evidence for magnetic interaction with chain Cu(1) atoms in the superconducting material is presented.