Gd3+ exchange interaction as measured by NMR in hydrogen-doped GdBa2Cu3O7H1.55.

Abstract

Proton NMR in nonsuperconducting ${\mathrm{GdBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$${\mathrm{H}}_{1.55}$ was measured at liquid-helium temperature by a spin-echo method. The negative shift of the resonance spectrum was found to be proportional to the dc magnetic field. This shift is shown to arise from the demagnetizing field due to a canted spin structure. The Gd exchange parameter is estimated to be J\ensuremath{\simeq}0.05 K, showing that the exchange energy is higher than the dipole one. Hydrogen doping has no effect on the gadolinium ordering temperature.