Two approaches attempted to overcome FePt nanoparticle sintering during the transformation to the high coercivity L10 phase, which currently limits the use of these nanoparticles in data storage media. High-pressure treatment of dilute nanoparticle solutions failed to prevent sintering due to surfactant decomposition above 360 °C. By pre-annealing nanoparticle monolayers to decompose the surfactant, and then coating with an immiscible SiO2 matrix, sintering was prevented with annealing temperatures up to 700 °C.