Dependence of Frequency and Magnetic Field on Self-Heating Characteristics of NiFe O Nanoparticles for Hyperthermia

Self-heating temperature-rising characteristics of nano-size controlled NiFe₂O₄ particles were analyzed as a function of applied frequency and magnetic field in order to investigate the physical principle of self-heating and to confirm the possibility for a real in vivo hyperthermia application. According to the magnetic properties of 35-nm size NiFe₂O₄ nanoparticles, it was confirmed that the physical mechanism of self-heating is mainly attributed to the hysteresis loss. In addition, it was found that the self-heating temperature was linearly increased by increasing frequency and was proportionally square to the applied magnetic field. The self-heating temperature was rapidly increased in an initial stage and then it reached to the maximum. The maximum self-heating temperature was controlled from 2.8degC to 72.6degC by changing the applied frequency and magnetic field. The corresponding product of the frequency and the strength of magnetic field H₀f was between 1.9times10⁸ Am^-1s^-1 and 13.4times10 ⁸ Am^-1s^-1. These values are in the biological safety and tolerable range for hyperthermia considering deleterious physiological response of human body during hyperthermia treatment