Particle Characterization. The specific surface area was determined by nitrogen adsorption (Brunauer-Emmett-Teller; BET method) at 77 K using a Tristar II Plus (Micromeritics, USA) after degassing for at least 3 hours at 110 ℃ under a flow of nitrogen gas. X-ray diffraction (XRD) patterns were obtained at ambient temperature with a MiniFlex X-ray diffractometer (Rigaku Europe, Germany) using Cu Kα1 radiation (1.5406 Å) and at 40 kV and 15 mA. The patterns were recorded between 10° and 80° 2θ at a step size of 0.01° 2θ and a scan speed of 2.00 deg min -1 . A DTex detector was used in narrow energy gap mode to suppress iron fluorescence background from the copper radiation. XRD data were analyzed using PDXL2 software (Rigaku Europe, Germany). All patterns were normalized relative to the intensity of the peak corresponding to the (311) crystal plane. The average crystal size (dXRD) of SPIONs was calculated by Rietveld refinement analysis using the PDXL2 software. Particle morphology was visualized by transmission electron microscopy (TEM) with Tecnai™ G2 Spirit BioTwin, (Thermo Fisher/FEI, USA) operating at 80 kV. The samples were suspended in 99.5% ethanol and deposited (as a 5 µL drop) on a 200-mesh copper grid (Ted Pella, USA) coated with formvar and carbon. The primary particle size distribution was measured by counting 360 and 394 particles of Zn0.5Fe2.5O4 and Mn0.5Fe2.5O4, respectively, using ImageJ software. The particle magnetization was recorded on a vibrating sample magnetometer (Lake Shore, USA) and a Physical Property Measurement System (Quantum Design, USA). Magnetization versus magnetic field was measured in the field range ±1000 mT at a constant temperature of 25 °C. The thermal dissipation of nanoparticle powders was measured using an oscillating magnetic field apparatus (Magnetherm; NanoTherics Ltd., UK).