(07B531) Cobalt driven enhancement of nanomagnetism in iron-oxide nanoparticles encapsulated in a synthetic ferritin shell

摘要

We have examined the effects of Co doping (0-12% relative to total metal) on the magnetic properties of iron-oxide nanoparticles incorporated in a synthetic ferritin shell. Mossbauer spectroscopy revealed that the nanoparticles consisted of a mixture of Fe_3O_4 and γ-Fe_2O_3, and that Co was integrated exclusively into the B-sites of the Fe_3O_4 phase. Cobalt doping resulted in the formation of Co_xFe_(3-x)O_4/γ-Fe_2O_3 nanoparticles with x = 0, 0.25, 0.51, 0.56, and 0.63. Magnetometry and susceptometry experiments showed that substantial enhancements in the coercivities, blocking temperatures and anisotropy constants of the magnetoferritin nanoparticles occurred for all Co doping levels. Our results show that the Co altered significantly the local atomic Fe magnetism and enhanced the magnetic nanoparticle anisotropy considerably.