Calculation of nuclear spin-lattice relaxation rate due to two-magnon scattering in YBa2Cu3O6

YBa₂Cu₃O₆ is known to be an antiferromagnetic insulator with high Neel temperature (T_N≈400≈500 K). The nuclear spin-lattice relaxation rate 1/T₁ due to two-magnon scattering is calculated, using values of ecchange integrals and anisotropy gap published in literature. We found approximately quadratic dependence of relaxation rate 1/T₁ on temperature for temperatures above 100 K. The value of 1/T₁, determined by low-energy magnons, is found to be inversely proportional to magnitude of gap in magnon spectrum.