Thermal Magnetic Effect of Needle-Shaped Gamma-Iron Oxide Nanoparticles in Low-Frequency Fields

The hyperthermic effect of spherical and needle-shaped iron oxide nanoparticles coated with oleic and citric acids in a low-frequency alternating magnetic field is studied. Measurements of their magnetic properties reveal the superparamagnetic properties of nanomagnetite and the presence of the hysteresis loop in maghemite. The heat release of dispersions is measured in the low-frequency range (1.0-5.2 kHz) and magnetic fields (8-31 mT). The results are used to calculate a quantitative characteristic, the specific absorption coefficient, and its dependence on the frequency and field strength. A substantial heat-release effect in low-frequency fields for needle-shaped magnetic particles is observed. It is shown that heat release in an aqueous medium is stronger than one in propylene glycol. Suspensions of such particles are promising for application in treating oncological diseases by means of magnetic hyperthermia.