Evaluation of magnetization dynamics influenced by Brownian relaxation in magnetic nanoparticles

Magnetic relaxations determine the magnetization properties of magnetic nanoparticles for biomedical applications such as the tracer of magnetic particle imaging. In this study, the magnetization dynamics influenced by the dynamics of the particle body as the easy axes of magnetic nanoparticles of different structures were evaluated measuring the magnetization curves, intensity of harmonic components in magnetization, and oscillation and orientation of the easy axis. To observe the effects of the Brownian relaxation associated with particle rotation, we prepared magnetic nanoparticles fixed with epoxy resin to inhibit the particle rotation and dispersed them in water where the particle rotation occurred. It is indicated that the Brownian relaxation observed as the particle oscillation and orientation significantly affected the magnetization dynamics of magnetic nanoparticles in the ferromagnetic regime