Will the Curie temp of a ferrofluid be the same as the Curie temp of just the ferrite it is composed of? Example - If I take CoFe2O4 and produce a ferrofluid from it, will the Curie temperature be the same as the pure ferrite?
The Curie temperature of ferro- or ferrimagnets is above a boliling temperature of most ferrofluids.
More important for properties of ferrofluids is the blocking temperature of ferrofluid nanoparticles, defined as Tb=KV/kb where K is the magnetic anisotropy constant, V is the particle volume and kb is Boltzmann constant.
Above Tb ferrofluid is in superparamagnetic state, below it exhibits strong magnetic properties.
Best regards, Bart
Dear Merlin,
Yes, the Curie temperature only corresponds to the small crystals (ferromagnetic nanoparticles) which have ferromagnetic order or superparamagnetic one depending of the size of the nanoparticles. The ferrofluids haven't a ferromagnetic order by themself, in fact they are paramagnetic because they order disapper when the external magnetic field is removed.
The magnetic fluid consists of magnetite nanoparticles, kerosene, surfactant. If you determine the Curie temperature, the kerosene will begin to boil. If you refill the powder of magnetite nanoparticles with a size of 2 nm, the Curie temperature will be 600K, and with a size of 20 nm, 810K. If you determine the temperature of magnetite the size of a pea, then it will be also 810 nm. This is an example of dimensional effects for nanoparticles.
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