What are ferrofluids?

Some articles on ferrofluids, ferrofluid:

Ferrofluid - Applications - Medicine
... In medicine, ferrofluids are used as contrast agents for magnetic resonance imaging and can be used for cancer detection ... The ferrofluids are in this case composed of iron oxide nanoparticles and called SPION, for "Superparamagnetic Iron Oxide Nanoparticles" There is also much ... It is based on the fact that a ferrofluid placed in an alternating magnetic field generates heat ...
Ferrofluid - Applications - Heat Transfer
... An external magnetic field imposed on a ferrofluid with varying susceptibility (e.g ... Ferrofluids are commonly used in loudspeakers to remove heat from the voice coil, and to passively damp the movement of the cone ... Since ferrofluids are paramagnetic, they obey Curie's law, thus become less magnetic at higher temperatures ...