Before discussing the role of the laser power in the measurements by Yew and coworkers, let us introduce the magnetism in Fe3O4 NPs. In Blaney, 2007, we can find the detailed description of magnetite (Fe3O4). A section of the article explores the bulk properties of it. Referring to Cornell and Schwertmann, 1996, Lee Blaney is evidencing a semi-conductor behavior, bordering the conductor (metallic) behavior, of the magnetite. A semimetallic behavior of magnetite is also supported by the relatively low bandgap (0.1 eV) of the material . The Curie temperature is at 850 K. Below the Curie temperature, we can find the magnetite as a ferrimagnetic material ; see our Appendix C for the other iron oxides). "When the Curie temperature is attained, a superparamagnetic behavior is observed". 850 K is the Curie temperature of the bulk material, and we are quite above the room temperature; however, if we consider the particles, as the particle size decreases, the behavior tends towards a paramagnetic or superparamagnetic magnetization. The decreasing of the particle size reduces ferrimagnetic behavior and enhances superparamagnetic behavior .