Antiferromagnetic Domains in RbMnF3

The indirect observation of domains in the cubic antiferromagnet RbMn${\mathrm{F}}_3$ through antiferromagnetic resonance is reported. Because of the cubic anisotropy of RbMn${\mathrm{F}}_3$, the equilibrium orientation of the magnetic sublattices is not in general unique, and the formation of antiferromagnetic domains may occur. The appearance of more than two branches in the antiferromagnetic resonance spectrum implies the existence of a multidomain structure. The probable orientations of domains, corresponding to local minima in the free energy, have been calculated for the case of a magnetic field applied along the [$11\overline{2}$] direction. Measurements were made on a single-crystal sample of RbMn${\mathrm{F}}_3$ at 4.2°K. For small values of applied field (<2000 Oe), the mode spectrum in the $X$-band region consisted of six branches. There is good agreement between the computed frequencies for the domains as a function of applied field and the experimentally observed values. The agreement implies that domain rotation takes place. A pronounced hysteresis in the resonance absorption, measured as a function of applied field, for certain resonances has been observed. The hysteresis has been attributed to domain-wall motion.