Understanding the Effect of Magnetic Field and Nanoparticle Concentration on Brownian Relaxation Time in Magnetic Nanofluids: A Semi-Analytical Model

Abstract

Abstract Magnetic nanofluids are used in many types of applications. Therefore, the dynamics of magnetic nanoparticle systems under the action of magnetic field were intensively studied, lately. Many studies related to biomedical applications consider the Brownian relaxation time independent from the magnetic field and nanoparticle concentration. This modelling assumption can lead to certain errors in the estimation of some parameters of interest. Thus, these errors also propagate in the determination of the effective relaxation time, which is of great importance in the estimation of some quantities of interest such as SAR (Specific Absorption Rate) or ILP (Intrinsic Loss Power Values) for magnetic hyperthermia. This paper presents a study of these errors starting from a semi-analytical model. Our experimental results can be useful to understand the mechanisms of magnetic relaxation of a nanofluid in various conditions and, above all, to create suitable numerical evaluation models.