AC Field Threshold Effect as a Key Factor toward the Efficient Heating of Fluids with NaFeO2 Magnetic Nanoparticles

Principal factors leading to the efficient alternating current (AC) field-induced heating of magnetic fluids are determined based on the results of magnetic and calorimetric measurements on NaFeO2 nanoparticles and their fluids. Features of the magnetic behavior are singled out, and characteristic magnetic parameters, such as the Curie and blocking temperatures, are determined for the NaFeO2 nanoparticles. The dependence of the fluid caloric properties on the AC magnetic field amplitude and nanoparticle concentration is analyzed. It is shown that the heating efficiency of the weakly coercive NaFeO2 nanoparticles displays an amplitude threshold character, and the heating rate is critically dependent on the AC magnetic field amplitude.