Mössbauer Effect in a Cubic Antiferromagnet near the Néel Point

Combined Mössbauer and magnetization measurements show that RbFe${\mathrm{F}}_3$ orders antiferromagnetically at ∼102°K and undergoes a transition to a state with a net magnetization at 87°K. In the antiferromagnetic region both the quadrupole coupling and hyperfine effective field can be described as arising from the exchange splitting of the low-lying spin-orbit triplet. The temperature dependence of the sublattice magnetization is in accord with a critical exponent $\beta \sim \frac{1}{3}$.