Determining the Néel and Brownian relaxation times in Co-Mn mixed ferrite nanoparticles

Cancer treatment by magnetic hyperthermia using superparamagnetic nanoparticles (SPM NPs) is in great attention in recent years. Unfortunately, there is no explicit dependence of the heating performance of NPs on the size, shape, or chemical composition. Nevertheless, all aspects modify the anisotropy constant, which is a crucial parameter to determine the Néel relaxation - one of the processes of heat generation by the SPM NPs. Half-polarized small-angle neutron experiments enable us to access the spatially resolved effective anisotropy constant and give us access to the hydrodynamic size of NPs, which are crucial parameters to determine Néel and Brownian relaxation times, respectively. Thus this study aims to unveil the magnetic structure of SPM NPs and correlate it with the magnetic NPs' heating performance.