Evaluation of easy-axis dynamics in a magnetic fluid by measurement and analysis of the magnetization curve in an alternating magnetic field

An understanding of the magnetic relaxation mechanism is critical to the medical application of magnetic nanoparticles. The temporal change in magnetization caused by an applied field can be evaluated by measuring the magnetization curves in the alternating fields. When magnetic nanoparticles are dispersed in a liquid, owing to magnetic torque, the Brownian relaxation influences the magnetization dynamics, in addition to the Néel relaxation. In this study, by evaluating the magnetization curve obtained by subtracting the magnetization curve corresponding to the solid from that of the liquid, the dynamics of the easy axis are observed with respect to the superparamagnetic nanoparticles.