Size determination of superparamagnetic nanoparticles from magnetization curve

The size distribution of superparamagnetic iron oxide nanoparticles in two powder samples is determined from the measured magnetization curve fitted by a core-shell model and a uniform model, both based on the Langevin function with a log-normal particle volume distribution. Different average sizes are evaluated from the fitting parameters and compared to those determined by other techniques. Conceptual discussions are presented on different models and approaches, from which the core-shell model fitting is recommended for the magnetic size determination of superparamagnetic nanoparticles.