Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO.

We report new results of a Fe Mössbauer study of hyperfine magnetic interactions in the layered multiferroic 3R-AgFeO demonstrating two magnetic phase transitions at T and T . The asymptotic value β   ≈  0.34 for the critical exponent obtained from the temperature dependence of the hyperfine field H (T) at Fe the nuclei below T   ≈  14 K indicates that 3R-AgFeO shows quasi-3D critical behavior.