Magneto-optical absorption in infrared region for magnetic fluid thin film

The magnetic field and wavelength dependences of the optical absorption coefficient, α, were measured in the infrared range for magnetic fluids containing Fe₃O₄ or MnZn ferrite particles. The absorption in the absence of magnetic fields is due mainly to the magnetic particles themselves. With increasing applied magnetic field, Δα decreases for the ordinary ray and increases for the extraordinary ray. This magnetic field dependence is attributed to the formation of chainlike clusters of a few colloidal particles (microclusters) whose length is much shorter than the wavelength of the infrared ray. In the Mn-Zn ferrite magnetic fluid, Δα for the ordinary and extraordinary rays increases gradually after a magnetic field is applied. The time dependence is caused presumably by growth into macroclusters whose length is comparable with the wavelength