Deviations from the Curie-law variation of magnetic susceptibility in antiferromagnetic nanoparticles - art. no. 132410

The temperature variation of the low-field magnetic susceptibility chi for antiferromagnetic nanoparticles of ferritin and ferrihydrite in the superpa ramagnetic regime is shown to follow the equation chi (-) chi (o) + (C/T). The theoretical basis for this equation is the low-field limit of the modif ied Langevin variation of the magnetization M given by M = MoL(mu H-p/k(B)T ) + chi H-a (H is the applied field, mu (p) is the magnetic moment/particle , and chi (a) is the antiferromagnetic susceptibility of the core). Self-co nsistent values of C, mu (p), and chi (o) are obtained for ferritin and fer rihydrite nanoparticles.