Spin Waves and Nuclear Magnetic Resonance Enhancement in NiF2Domain Walls

Abstract

We have obtained the allowed magnetic resonance modes or spin waves in the canted antiferromagnet Ni${\mathrm{F}}_2$ in the presence of a Bloch wall. Our formulation includes the anisotropy and exchange energies of the crystal together with characteristics of the wall such as its stiffness, mass, and viscosity. From the dispersion equations, we show that there exists a bound wall excitation branch having a lower excitation energy than the free spin wave excitation branch. Further, we have calculated the effective nuclear magnetic resonance field enhancement due to the bound wall excitation branch as a function of the parameters of the crystal and the Bloch wall and shown that our results are equivalent to those obtained experimentally. Finally, we compare this enhancement with that of a pure antiferromagnet—demonstrating that the canting is essential for this process.