The Mo¨ssbauer linewidth broadening of superparamagnetic particles of ferric hydroxysulfate, near the point where the paramagnetic lines begin to appear, has been investigated as a function of temperature. This behavior is explained by a geometric picture of an assembly of magnetically ordered single‐domain particles whose magnetic moments move within an asymmetric double‐well potential. A relaxation model is presented which combines the conventional theory of superparamagnetism with an exponential distribution of energy barriers.