Magnetic nanoparticles that display high saturation magnetization and high magnetic susceptibility are of great interest for medical applications. Nanomagnetite is particularly desirable because it displays strong ferrimagnetic behavior, and is less sensitive to oxidation than magnetic transition metals such as cobalt, iron, and nickel. For in-vivo applications, it is important that well-defined organic coatings surround the nanomagnetite particles. It is rationalized that this will prevent any aggregation of the nanoparticles in-vivo, and may also enable efficient excretion and protection of the body from toxicity.