Exchange Interactions and Raman Scattering from Spin Excitations in RbNiF3

The Raman spectrum of RbNi${\mathrm{F}}_3$ has been observed over the temperature range 15-300°K, using an argon laser. In addition to vibrational Raman lines, a single strong line of magnetic origin, persisting well above $T_c$, is observed. A proposed ion pairing and scattering mechanism leads to a set of exchange parameters consistent with several other magnetic properties in RbNi${\mathrm{F}}_3$.