posted on 2015-11-10, 00:00authored byQian Zhang, Idoia Castellanos-Rubio, Rahul Munshi, Iñaki Orue, Beatriz Pelaz, Katharina Ines Gries, Wolfgang J. Parak, Pablo del Pino, Arnd Pralle
This study provides a guide to maximizing
hysteretic loss by matching
the design and synthesis of superparamagnetic nanoparticles to the
desired hyperthermia application. The maximal heat release from magnetic
nanoparticles to the environment depends on intrinsic properties of
magnetic nanoparticles (e.g., size, magnetization, and magnetic anisotropy)
and extrinsic properties of the applied fields (e.g., frequency and
field strength). Often, the biomedical hyperthermia application limits
flexibility in settings of many parameters (e.g., nanoparticle size
and mobility, field strength, and frequency). We show that core–shell
nanoparticles combining a soft (Mn ferrite) and a hard (Co ferrite)
magnetic material form a system in which the effective magnetic anisotropy
can be easily tuned independently of the nanoparticle size. A theoretical
framework to include the crystal anisotropy contribution of the Co
ferrite phase to the nanoparticle’s total anisotropy is developed.
The experimental results confirm that this framework predicts the
hysteretic heating loss correctly when including nonlinear effects
in an effective susceptibility. Hence, we provide a guide on how to
characterize the magnetic anisotropy of core–shell magnetic
nanoparticles, model the expected heat loss, and thereby synthesize
tuned nanoparticles for a particular biomedical application.