Superparamagnetic behavior of non-interacting antiferromagnetic ferritin nanoparticles.

Ferritin is an important biological system and found in blood of living organisms. Inorganic cores of this material are 8 nm in size. The cores are surrounded by protein shells which reduce interparticle interaction. Particle size distribution present in ferritin is determined from transmission electron micrograph. This distribution can be described by a log normal distribution function. The magnetic field (0–70 kG) dependence of the magnetization at different temperatures are analyzed considering the estimated particle size distribution. The resulting mean particle magnetic moment is temperature independent and equal to 310 μ B. Saturation magnetization and antiferromagnetic susceptibility of ferritin decrease with increasing temperature. • Ferritin contains an antiferromagnetic inorganic core surrounded by a protein shell. • Langevin function assumes that all particles have same magnetic moment. • Particle size distribution present in a sample of ferritin is determined from transmission electron micrograph. • Magnetization data on ferritin in superparamagnetic region are analyzed considering a distribution in particle size. [ABSTRACT FROM AUTHOR]