Heating Efficiency by Energy Absorption

The heat dissipation by magnetic nanoparticles under the influence of an alternating magnetic field is used in magnetic hyperthermia for cancer treatment [88]. To evaluate the heating properties of the materials, they should be characterized under an AMF. 

To analyze the energy absorption by the material and the subsequent heat transference to the media by the magnetic moment rotation under an AMF, the specific absorption rate (SAR) or specific loss power (SLP) can be determined  

Chastellain et al. confirmed the sensitivity of the power loss with respect to the size distribution, comparing power losses of silica-iron oxide nanocomposites synthesized by different routes [92]. Although for biomedical applications iron oxides are the main materials being studied because of their low toxicity, several studies have also evaluated the role of other materials for hyperthermia such as manganese perovskite nanoparticles [33]. The heating properties of several ferrites synthesized by sol-gel (Fe, Li, Ni/Zn/Cu, Co, Co/Ni, Ba, and Sr ferrites) have also been characterized [93]. However, in this kind of studies, it is complicated to isolate the effect of the composition on the heating properties of the material from other factors that may influence as well, such as the particle size or size distribution. 

Other parameters such as the particle shape and the spatial organization of the particles will have an effect on the heating capacity of the magnetic materials through their dependence on the magnetic anisotropy and interparticle magnetic interactions, respectively. 

Sol-gel processing has a long track record in producing useful materials for magnetic applications, in particular, magnetic nanoparticles and thin films. 

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