A dynamic hysteresis meter for studying ferrofluids designed for magnetic hyperthermia

An AC magnetometer system is developed to determine the specific absorption rate (SAR) of ferrofluids designed to work in the range of interest for magnetic hyperthermia. The experimental setup contains a set of configurable RL coil sensors (resistance plus inductance) to obtain the inner area of the dynamic hysteresis loops of colloidal dispersions, which are stimulated using a multi-range alternating magnetic field generator. This magnetometer is suitable for covering the frequency band of 100–450 kHz, and special considerations concerning sample size and placement inside the magnetic field region are taken into account. The performance of the system is tested using a ferrofluid of water-dispersed iron oxide nanoparticles. The SAR determined with the developed system is compared with that obtained using the typical calorimetric procedure. The observations are consistent with both kinds of measurement, and also coincide with the results for other previously reported experimental systems. (paper)