We explored the reliable control of high-efficiency specific-loss power (SLP) using magnetic nanoparticles in the vortex state, where the value of power is one order of magnitude higher than those of the conventional mechanisms of SLP reported thus far. The underlying mechanism is based on the precession of a single vortex core and subsequent dissipation due to the intrinsic damping when the vortex-state spheres are resonantly excited. Owing to the dynamic characteristics of vortex-state nanoparticles, the resonant excitation of vortex-core precession is variable with particle size as well as tunable by the size-specific resonant frequency and strength of ac magnetic fields applied to the particles. The ac magnetic-field energy absorbed by the particles can be converted very efficiently to other energy forms such as heat. We derived, semi-analytically and by micromagnetic simulations, the quantitative relationships of the SLP quantity with the particle size and intrinsic damping constant of nanoparticles, and with externally controllable parameters including the frequency and strength of ac magnetic fields and dc magnetic-field strength. This work provides a reliable means of control as well as an optimal design of high-value SLPs for high-efficiency hyperthermia bio-applications.

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