Magnetic properties of the antiferromagnet RbMnF3 have been studied. Below T^, the magnetic ions order into a two-sublattice system with the spins antiparallel. RbMnFo exhibits high exchange and low anisotropy; the form of the anisotropy surface is cubic. Consequently, for applied DC magnetic fields less than about 3000 oe, the static equilibrium position of the sublattice magnetization is, in general, multivalued. Measurements of the DC susceptibility x have been made on powder and single

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... al specimens of RbMnF~ for the range of applied field 0 to 12 koe and over the temperature range 4.2 to 300°K. The observed value of T^, was about ten degrees higher than the previously published value. When plotted as a function of applied field, Xn i n shows no abrupt discontinuity analogous to the spin flopping exhibited by uniaxial antiferromagnets. A simple model, in which H_ r and M are restricted to the (110) plane, has enabled solutions of the static equilibrium problem to be obtained. X-band resonance experiments are reported, and a resonance theory is presented which incorporates the equilibrium solutions. The predicted antiferromagnetic resonance spectrum shows reasonable agreement with the experimental data. The possibility of parallel pumping spin waves in RbMnFg is considered, and an attempt to measure the spin wave linewidth is described.