Controlling Magnetization Reversal and Hyperthermia Efficiency in Core–Shell Iron–Iron Oxide Magnetic Nanoparticles by Tuning the Interphase Coupling

Abstract

Magnetic particle hyperthermia, in which colloidal nanostructures are exposed to an alternating magnetic field, is a promising approach to cancer therapy. Unfortunately, the clinical efficacy of hyperthermia has not yet been optimized. Consequently, routes to improve magnetic particle hyperthermia such as designing hybrid structures comprised from different phase materials are actively pursued. Here we demonstrate enhanced hyperthermia efficiency in relative large spherical Fe/Fe-oxide core/shell nanoparticles through the manipulation of interactions between the core and shell phases. Experimental results on exemplary samples with diameters in the range 30-80 nm indicated a direct correlation of hysteresis losses to the observed temperature elevation rate with a maximum efficiency of around 0.9 kW/g. The absolute particle size, the core/shell ratio, and the interposition of a thin wüstite interlayer, are shown to have powerful effects on the specific absorption rate. By comparing our measurements to micromagnetic calculations we have unveiled topologically non-trivial magnetisation reversal modes under which interparticle interactions become negligible, aggregates formation is minimized, and the energy that is converted into heat is increased. This information has been overlooked till date and is in stark contrast to the existing knowledge on homogeneous particles.

Embracing Defects and Disorder in Magnetic Nanoparticles

“…Inserting a paramagnetic FeO interlayer spacer between Fe core and iron oxide shell in layered iron oxide nanoparticles led to magnetostatic interactions between the core and the shell and enhanced magnetic hyperthermia performance. [ 73 ] Recently, trimagnetic Fe 3 O 4 ‐CoO‐Fe 3 O 4 core–shell–shell nanoparticles have been developed via seed‐mediated thermal decomposition synthesis. Hard–soft exchange couplings at Fe 3 O 4 ‐Co doped ferrite and Co‐doped ferrite‐Fe 3 O 4 interfaces largely influenced the superparamagnetic blocking temperature and magnetization hysteresis loops.…”

A comparative investigation of normal and inverted exchange bias effect for magnetic fluid hyperthermia applications

“…Presently, researchers are putting more emphasis on enhancing the SAR value through the bi-magnetic CS NPs with two different magnetic phases. This displays an exchange bias (EB) coupling phenomenon between the core and shell materials which results in tuning several magnetic properties of the NPs 11 – 14 . EB effect for a particular system consisting of AFM and FiM/FM materials arises when uncompensated AFM spins are usually pinned up with the spins of FiM phase at the magnetically interface surface,which in turn leads to hysteresis loop shift and amplification of coercivity 15 .…”

Mapping the Magnetic Coupling of Self-Assembled Fe3O4 Nanocubes by Electron Holography

“…These results indicate a promising way to increase the hyperthermia performance by assembling cubic particles in elongated chains. On the heels of our previous article, here we use electron holography experiments to access and map the magnetic configuration of Fe 3 O 4 cubic nanoparticles whose average diameter of 40 nm is expected to be close to the 180° domain wall width [ 12 ], thus may be promoting the presence of vortex pseudo-single-domain configurations [ 13 , 14 ].…”