Hysteresis Power-Loss Heating of Ferromagnetic Nanoparticles Designed for Magnetic Thermoablation

We have fabricated ferromagnetic Fe-oxide nanoparticles as a candidate of hysteresis-loss heating materials used for hyperthermia and thermoablation and examined heating abilities. The coercivities were controlled in a range between 50 Oe and 240 Oe. The temperature-rising characteristics were examined for randomly oriented solid nanoparticles by applying a 17-kHz ac magnetic field with an amplitude up to 550 Oe. A temperature rising rate DeltaT/Deltat was proportional to the square of the peak magnetic field H ₀ in the lower H ₀ region; however, the relation dose not hold at higher H ₀. The maximum loss power was obtained to be 4 W/g, which is smaller than the value expected from the minor loop experiment (13.7 W/g). The reason for small heating capability is discussed.