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

VALDÉS, DANIELA PAOLA; LIMA,, ENIO; ZYSLER, ROBERTO DANIEL; GOYA, GERARDO FABIÁN; DE BIASI, EMILIO

Physical Review Applied

American Physical Society

Año: 2021 vol. 15 p. 44005 - 44005

Efforts by numerous research groups haveprovided a deeper insight into the physical mechanisms behind the powerabsorption of single-domain magnetic nanoparticles inmagnetic-fluid-hyperthermia applications and theoretical models now account forthe main experimental observations. However, the role of all parametersrelevant to the magnetic relaxation remains a matter of debate. Here, we employa nonlinear model for the magnetic relaxation of single-domain magneticnanoparticles with uniaxial effective anisotropy and evaluate the influence ofparticle-intrinsic parameters as well as experimental conditions on the powerabsorption of both noninteracting and interacting systems (linear arrangements).These effects are assessed through the enclosed hysteresis area of themagnetization loops as a function of relative anisotropy hK (the anisotropyfield with respect to the amplitude of the ac field), i.e., the ?area curve? ofthe system. These curves can be divided into four regions with distinctmagnetic responses and boundaries that depend on the particle size, frequencyof the applied field and interactions. Interactions change the effectiveanisotropy of the system and shift the area curve towards lower hK values. Forthe low relative anisotropy range, dipolar interactions increase the area ofthe hysteresis loops [thus, the specific power absorption (SPA)], while theyare detrimental or produce nonsignificant effects for the range of highrelative anisotropy. Our study resolves seemingly contradictory results ofinteraction effects in linear arrangements recently reported in the literature.Simulations of randomly oriented particles and chains were contrasted with theoriented cases. An analytical approach and the thermal interpretation of itsvalidity range are discussed, both aimed at the design of nanoparticles and thechoice of the experimental conditions for optimal heating. We find that systemswith low-thermal-fluctuation influence are better candidates for theapplication due to their high SPA values.