Structural, magnetic and toxicity studies of ferrite particles employed as contrast agents for magnetic resonance imaging thermometry

•Mg1−xZnxFe2O4 and Cu1−xZnxFe2O4 ferrites particles were fabricated.•Particles show strong temperature variation of magnetization near body temperature necessary for MRI thermometry.•Rietveld analysis allowed to determine cations distribution.•MgZn ferrites are more suitable from the toxicology point of view for MRI thermometry. We carried out comprehensive structural, magnetic and toxicity studies of Mg1−xZnxFe2O4 and Cu1−xZnxFe2O4 ferrites that we plan to use as contrast agents for magnetic resonance-imaging thermometry. Samples were prepared by a standard ceramic technique. Their structural properties were investigated with an x-ray diffraction system, and data was analyzed using the Rietveld method that allowed us to determine cations distribution. Magnetic properties of MgZn and CuZn ferrites were studied using a superconducting quantum interference device magnetometer, a vibrating sample magnetometer, and Mössbauer spectrometer. Magnetometry measurements were cross-correlated with XRD results and compared with magnetic properties determined by Mössbauer spectroscopy, allowing us to understand the magnetic structure of studied ferrites. The temperature dependent magnetic measurements were used as guidance to select the most suitable MgZn and CuZn ferrites compositions for MRI thermometry near human body temperature. The inflammation studies indicated that MgZn ferrites are more suitable from the toxicology point of view for MRI thermometry.