MAGNETIC HYSTERESIS ANOMALIES IN FERRITIN

Ferritin, an antiferromagnetic nanoparticle with a net magnetic moment , exhibits some unusual magnetic behavior. Above its blocking temperat ure, T-B approximate to 12 K, the magnetization can be fit with the La ngevin function only by including an additional linear term. The satur ation moment decreases linearly with increasing temperature, and sugge sts an ordering temperature of about 460 K. Below T-B, both zero-field -cooled and field-cooled hysteresis loops exhibit large coercivity (si milar to 1800 Oe) and irreversibility in the loops is found up to H=35 kOe. An exchange field H-e of few hundred Oe is observed at low tempe ratures. The dependencies of H-e and H-c on temperature were also stud ied.