Heat generation in agglomerated ferrite nanoparticles in an alternating magnetic field

LIMA; DEBIASI; VAZQUEZ MANSILLA; SALETA; GRANADA; TROIANI; EFFENBERGER; ROSSI; RECHENBERG; ZYSLER

JOURNAL OF PHYSICS - D (APPLIED PHYSICS)

IOP PUBLISHING LTD

Lugar: Londres; Año: 2013 p. 1 - 13

0022-3727

The role of agglomeration and magnetic interparticle interactions in heat generation ofmagnetic ferrofluids in an ac magnetic field is still unclear, with apparent discrepancy betweenthe results presented in the literature. In this work, we measured the heat generating capabilityof agglomerated ferrite nanoparticles in a non-invasive ac magnetic field with f = 100 kHzand H0 = 13 kAm−1. The nanoparticles were morphologically and magneticallycharacterized, and the specific absorption rate (SAR) for our ac magnetic field presents a cleardependence on the diameter of the nanoparticles, with a maximum SAR = 48Wg−1 for15 nm. Our agglomerated nanoparticles have large hydrodynamic diameters, thus themechanical relaxation can be neglected as a heat generation mechanism. Therefore, wepresent a model that simulates the SAR dependence of the agglomerated samples on thediameter of the nanoparticles based on the hysteresis losses that is valid for the non-linearregion (with H0 comparable to the anisotropy field). Our model takes into account themagnetic interactions among the nanoparticles in the agglomerate. For comparison, we alsomeasured the SAR of non-agglomerated nanoparticles in a similar diameter range, in whichN´eel and Brown relaxations dominate the heat generation.