Comment on "Ultrathin Interface Regime of Core-Shell Magnetic Nanoparticles for Effective Magnetism Tailoring"

There has been renewed interest in the use of magnetic nanoparticles to convert high frequency electromagnetic energy into heat. During the last decade, numerous examples in the field of catalysis, lightweight thermoplastic composites for aeronautical and automotive engineering, and biomedical applications as well, have flourished. In a recent Letter "Ultrathin Interface Regime of Core-Shell Magnetic Nanoparticles for Effective Magnetism Tailoring", Moon et al. DOI: 10.1021/acs.nanolett.6b04016 claim to have observed a new interface spin canting phenomenon in core-shell ferrrites that pushes heating efficiencies above 10,000 W/g. If this were true, it represents new opportunities for further tailoring nanoscale agents to be used in drug delivery and selective destruction of tumours by hyperthermia. But here I argue that these claims are inconsistent with the facts of physics.