Optical transmission of an iron nanoparticle ferrofluid has been investigat
ed as a function of incident optical wavelengths between 450 and 700 nm and
applied magnetic fields up to 200 Oe. The transmittance decreases as the t
hickness and concentration of the Fe ferrofluid films increase. This effect
is more manifest with shorter incident wavelength. The decrease of transmi
ttance for sample prepared by electrochemical method is much more rapidly t
han that of samples prepared by laser ablation technique. However, the magn
etic field effect for these samples is vise versa. The aspect ratio of the
Fe nanoparticles we prepared is roughly between 1 and 2. The decrease of th
e transmittance between 575 and 450 nm is explained by a classical electros
tatic calculation based on the Mie/Drude formalism. (C) 1999 American Insti
tute of Physics. [S0021-8979(99)43508-X].