Influence of Damping Constant on Models of Magnetic Hyperthermia

In magnetic hyperthermia, the effectiveness for tumour cell destruction is measured by the specific loss power. Theoretically, within the medically accepted ranges for the amplitude and frequency of the applied magnetic field, if energy losses in nanofluids occur through magnetic relaxation processes, the specific loss power is calculated based on the linear response theory. In this theory, the specific loss power depends on the effective magnetic relaxation time of the colloidal nanoparticle system which involves either the Brownian relaxation time or the Ned relaxation time. All theoretical approaches to the Ned relaxation time show that it depends directly on the diffusional relaxation time and inversely on the smallest non-vanishing eigenvalue of the Fokker-Planck equation, where the damping constant is expressed one way or another by a value, generally unknown, which in most cases is approximated. This paper shows through a numerical experiment how the damping constant influences the specific loss power, referring to some benchmarks on how to choose the most accurate value of this constant in the case of magnetite nanoparticles, mostly used in magnetic hyperthermia applications. Following an uninspired choice of the damping constant value, the simulated or calculated data can deviate from the experimentally determined data, even if, in general, the model is correct and as close as possible to reality.