ABSTRACT
This chapter is concerned with the mechanisms of energy dissipation by magnetic nanoparticles (MNPs) in oscillating magnetic fields. We begin by motivating the content with a brief review of examples of biomedical applications of MNP heating. Then we describe the basic theory of the relaxation mechanisms of MNPs. Finally, we describe the mechanisms of energy dissipation by single-domain MNPs in oscillating magnetic fields.
Because of the advantages of their small size and superparamagnetic properties, many biomedical applications of MNPs rely on single-domain particles. This is motivated by a need to satisfy size constraints imposed by biological systems (e.g. to penetrate into tumors, particles should be smaller than 100 nm) and by colloidal stability considerations that indicate that particles with cores much larger than 20 nm would settle out of suspension due to the action of gravity. As such, in this chapter we discuss the theory applicable for energy dissipation by single-domain MNPs. We note that for larger particles other mechanisms may occur, such as hysteresis heating (Carrey, Mehdaoui, and Respaud 2011), but those mechanisms will not be discussed here.
