For cancer therapy with magnetic hyperthermia by using magnetic nanoparticles (MNPs) 1, 2, alternating magnetic fields (AMF) H_AC, typically sinusoidal wave, can deliver the magnetic energy into the deeper location in the body.
In this study, we proposed a highly effective heat generation method for the MNPs by the application of an ultra-short pulse. We numerically evaluated the heating power with a variety of parameters, such as pulse width, field amplitude, and frequency 3. Figure 1 shows effective magnetic hyperthermia with the ultra-short pulse magnetic field (Fig.1 (a)). The hysteresis curve and magnetization dynamics clearly indicate larger energy dissipation (Figs. 1 (b) and (c)). Figure 2 shows the energy dissipation and efficiency 4, 5 on the two-dimensional parameter space of field strength and duty ratio. Hysteresis loss and the input energy increases increasing with field strength and duty ratio (Figs. 2(a) and (b)) and there is a large efficiency power condition (Fig.2 (c)). To evaluate the effective heat generation and practical temperature increment, a larger imaginary part of magnetic susceptibility (χ^{’’} > 30) and specific loss power (SLP > 10⁵ W/kg) are required (Figs. 2 (d) and (e)). In addition, larger intrinsic loss power (100 nHm²/kg) is achieved (Fig. 2 (f)). Finally, we found the optimal condition of applied AMF (duty ratio = 1.2% and H_AC = 16 kA/m) considering the practical uses. The results indicate that magnetic harmonics signals with a higher frequency range significantly enhance the heat generation of MNPs. We explore further studies of the development of an effective pulse generator for clinical applications and evaluation of the heating effect in animal experiments.