Static and Dynamic Magnetic Response in Ferrofluids

Ferrofluids are technologically important for a variety of applications ranging from biomedicine, hydraulics, to power generation. They are also model systems for the investigation of physics of relaxation phenomena in magnetic nanoparticles. We have done systematic DC and AC magnetization studies of ferrofluids composed of Fe3O4 and CoFe2O4 nanoparticles mean size 14 nm suspended in hexane and dodecane, respectively. The blocking temperature was just above hexane and much below dodecane the carrier fluid freezing temperatures providing interesting regimes to study the relaxation mechanisms associated with the fluid and frozen states.