Role of Interactions in the SAR and Determination of the Temperature Profile in Magnetic Hyperthermia
Résumé
Magnetic hyperthermia consists in converting electromagnetic energy into heat by applying an external AC magnetic field to an assembly of magnetic nanoparticles. This results in a very localized temperature rise which can be useful in medicine and catalysis. However, several fundamental aspects must be fully analyzed in order to better understand how to control the temperature space-time profile within magnetic nanoparticle assemblies. In particular, in view of building multi-scale sensible models for future developments in magnetic hyperthermia, two important points need to be clarified: 1) the role of dipolar interactions (DI) in the optimization of the specific absorption rate (SAR), and 2) the heat diffusion within the assembly and through its interface with the surrounding environment. Here, we address comprehensively these two issues. We first show how to determine the SAR of the assembly both semi-analytically (weak DI [1,2]) and numerically (higher concentration – strong DI [3]) to systematically investigate the effect of density and non-linear terms. The obtained SAR then serves as a source in the balance equation for heat diffusion, taking account of Newton’s law of cooling at the interface between the sample and its immediate vicinity [4]. The temporal profile of the temperature elevation is confronted with experimental data for maghemite and magnetite ferrofluids, providing a basis for the rationalization of the dependence of the Newton coefficients on the relevant physical parameters.Acknowledgments The authors acknowledge the support of the French Agence Nationale de la Recherche (ANR), ANR “NanoHype”, under grant ANR-21-CE09-0043-01References[1]J.-L. Dejardin, F. Vernay, M. Respaud, H. Kachkachi, J. Appl. Phys. 121, 203903 (2017)[2]J.-L. Déjardin, F. Vernay, H. Kachkachi, J. Appl. Phys. 128, 143901 (2020)[3]V. Russier, J. J. Alonso, I. Lisiecki, A.T. Ngo, C. Salzemann, S. Nakamae, and C. Raepsaet, Phys. Rev. B 102, 174410 (2020)[4]J.-L. Déjardin, and H. Kachkachi, Journal of Magnetism and Magnetic Materials, 556, 169354 (2022)