title: An adapted Coffey model for studying susceptibility losses in interacting magnetic nanoparticles.
abstract: BACKGROUND
  Nanoparticles can be used in biomedical applications, such as contrast agents for magnetic resonance imaging, in tumor therapy or against cardiovascular diseases. Single-domain nanoparticles dissipate heat through susceptibility losses in two modes: Néel relaxation and Brownian relaxation.
  
  
  RESULTS
  Since a consistent theory for the Néel relaxation time that is applicable to systems of interacting nanoparticles has not yet been developed, we adapted the Coffey theoretical model for the Néel relaxation time in external magnetic fields in order to consider local dipolar magnetic fields. Then, we obtained the effective relaxation time. The effective relaxation time is further used for obtaining values of specific loss power (SLP) through linear response theory (LRT). A comparative analysis between our model and the discrete orientation model, more often used in literature, and a comparison with experimental data from literature have been carried out, in order to choose the optimal magnetic parameters of a nanoparticle system.
  
  
  CONCLUSIONS
  In this way, we can study effects of the nanoparticle concentration on SLP in an acceptable range of frequencies and amplitudes of external magnetic fields for biomedical applications, especially for tumor therapy by magnetic hyperthermia.
authors.affiliation: "Politehnica" University of Timisoara, Department of Electrical Engineering and Industrial Informatics, Piata Victoriei Nr. 2, 300006 Timisoara, jud. Timis, Romania.
authors.forename: Mihaela
authors.initials: M
authors.lastname: Osaci
authors.affiliation: University "Mediterranea" of Reggio Calabria, DICEAM, Via Graziella Feo di Vito, I-89100 Reggio Calabria, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Cacciola
keywords: hyperthermia; magnetic nanoparticles; relaxation process; specific loss power; susceptibility losses