Abstract
The transmission of light through CoFe2O4 ionic aqueous ferrofluids under different magnetic fields is measured. The results show that the transmission intensity increases quickly as soon as the magnetic field is applied, and then weakens with time. Both the initial increase and following decrease of the transmission intensity are proportional to the volume fraction Φv of CoFe2O4 particles in the ferrofluid and the magnetic field strength B. Once the magnetic field is removed, the transmission intensity rises rapidly to a stable value, which is inversely proportional to the Φv and B, and is less than the value before the magnetic field was applied. These results indicate that there exists a dynamical process that the chains of magnetic particles in the ferrofluid form, join, and then break.