Controlling magnetisation's reversal mechanism and hyperthermia efficiency in core/shell magnetic nanoparticles by tuning the interphase coupling

TL;DR

This study enhances magnetic hyperthermia efficiency in Fe/Fe-oxide core/shell nanoparticles by tuning interphase interactions, revealing new magnetisation reversal modes that improve heat generation for cancer therapy.

Contribution

It demonstrates how manipulating core/shell interactions and interphase properties in magnetic nanoparticles improves hyperthermia performance, introducing novel magnetisation reversal modes.

Findings

Maximum hyperthermia efficiency of ~0.9 kW/g achieved.

Interphase tuning significantly affects heat absorption.

New magnetisation reversal modes reduce interparticle interactions.

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 w\"ustite 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.