Role of Anisotropy, Frequency, and Interactions in Magnetic Hyperthermia Applications: Noninteracting Nanoparticles and Linear Chain Arrangements

DANIELA P. VALDÉS; ENIO LIMA JR.; ROBERTO D. ZYSLER; GERARDO F. GOYA; EMILIO DE BIASI

Svetlogorsk

Conferencia; IV International Baltic Conference on Magnetism 2021 - IBCM 2021; 2021

The enhancement of the specific power absorption (SPA) of magnetic nanoparticles(MNPs) for magnetic fluid hyperthermia applications is currently focused on the design of MNPswith tuned properties or searching for the optimal experimental conditions for a particular system.However, the role of all parameters relevant to the relaxation still remains a matter of debate.We modify a nonlinear model for the magnetic relaxationof single-domain magnetic nanoparticles with uniaxial effectiveanisotropy [1] and evaluate the influence of particle-intrinsicparameters as well as experimental conditions on the powerabsorption of both noninteracting and interacting systems (linearchain arrangements) [2]. These effects are assessed through thenormalized enclosed hysteresis area a of the magnetization loopsas a function of relative anisotropy hK (the anisotropy field withrespect to the amplitude of the ac field), i.e., the ?area curve? ofthe system (see Figure 1). These curves can be divided into fourregions (I-IV) with distinct magnetic responses and boundariesthat depend on the particle size, frequency of the applied field,orientation of the anisotropy axes and interactions. Interactionschange the effective anisotropy of the system and shift the areacurve towards lower hK values. For the low relative anisotropyrange, dipolar interactions increase the area of the hysteresis loops (thus, the SPA) while they aredetrimental or produce nonsignificant effects for the range of high relative anisotropy. Our studyresolves seemingly contradictory results of interaction effects in linear arrangements recentlyreported in the literature.An analytical approach and the thermal interpretation of its validity range are detailed, bothaimed at the design of nanoparticles and the choice of the experimental conditions for optimalheating. We conclude that systems with low-thermal-fluctuation influence are the best candidatesfor the application due to their high SPA values.