Influence of hydrogen on 123 and 124 HT_c superconductors studied by Cu NMR and NQR

The antiferromagnetic compounds produced by the reaction of the 123 and 124 HT_c superconductors with hydrogen are studied by nuclear resonancee of copper. For the 123 compounds two reactions are possible, the reduction by hydrogen which leads to the normal antiferromagnetic YBa₂Cu₃O₆, and the solution of hydrogen in YBa₂Cu₃O₇ which forms a different antiferromagnetic structure with hydrogen concentration of more than 2 H mol^-1. Both structures can be distinguished by the nuclear quadrupole resonance spectra of the Cu(1) sites and the nuclear magnetic resonance spectra in the hyperfine field of the antiferromagnetic state. By using samples containing Gd at the place of Y we can prove that only the Cu(2) sites carry permanent magnetic moments. In the hydrogen loaded YBa₂Cu₄O₈ the situation is similar with the antiferromagnetic order limited to the Cu(2) sites.