Low-TemperatureCr53NMR in a Ferromagnetic CrBr3Single Crystal

The properties of the ${\mathrm{Cr}}^{53}$ NMR in a single crystal of ferromagnetic Cr${\mathrm{Br}}_3$ were studied at low temperatures. From the dependence of the observed resonances on the orientation of the magnetic field with respect to the easy axis of magnetization and the magnitude of the enhancements of the driving rf field it is shown that all of observed spectra must arise from nuclei belonging to spins that, in the main, are at the center and edge of 180° walls, in the unsaturated state. Using a model which incorporates a position-dependent linewidth within the wall a reasonable simulation of the observed spectra is made. The predicted dependence of the domain rotation enhancement, above saturation, on the magnitude and orientation of the external field is observed. Some implications of these results for other NMR studies in ferromagnets are discussed.