Magnetite ferrofluid with high specific absorption rate for application in hyperthermia

A magnetite ferrofluid coated by dextran with a high specific absorption rate (SAR) of 75 W/g in an AC field of 55 kHz and 200 Oe was prepared by the gel crystallization method with ultrasonic treatment. For comparison, uncoated magnetite particles with a mean diameter of 50 nm were also fabricated. Several possible mechanisms such as Brownian, Neel and diffusion relaxation processes on heating effects and their influence on SAR are discussed. Several factors which can increase the value of SAR were discussed, including dextran coating, ultrasonic treatment, proper particle size and the presence of defects and disorder in the particles.