Nuclear Magnetic Resonance within an Antiferromagnetic Bloch Wall

In a previous paper by the author, the bound spin wave excitation spectrum existing within an antiferromagnetic Bloch wall was derived. We calculate, here, the effect of this energy excitation spectrum on the linewidth and relaxation times of the magnetic resonance of nuclei existing within the wall. A relaxation time $T_1$, caused by excitation of the transverse components of the electron spin by the resonance field, is shown to be smaller in antiferromagnets than in ferromagnets due to the larger minimum wall excitation energy. The linewidth due to indirect coupling of the nuclear spins through the virtual excitation of a spin wave, however, proves to be increased by the square root of the ratio of the anisotropy to the stiffness parameters compared to the uniform antiferromagnet. This may account for the rather large linewidths observed in nuclear magnetic resonance experiments in antiferromagnets. A second nuclear linewidth, resulting from the variation of the deviation of the longitudinal component of the electron spin from the center to the edge of the wall is also calculated. Numerical results are obtained and, where possible, compared with experiment.