The singlet ground state antiferromagnet RbFeBr3shows an induced moment behavior at low temperatures and orders antiferromagnetically atTN=5.5 K. A second magnetic phase transition takes place at 2.0 K. The magnetic phase between 2 K <T<5.5 K may be partially ordered while atT<2.0 K a modified triangular magnetic structure will be adopted. The temperature dependence of the magnetic excitations at the soft mode pointQ(1/3,1/3,1) show a switching of intensity at 2 K. Above 4 K the magnetic excitations start to broaden. AboveTNthe magentic excitations show a renormalization behavior. The temperature dependence of renormalization is well described by the theoretical predictions of the DCEFA model.