Dichromatic properties of a magnetic fluid thin layer

In the paper, we investigate spectral dependence of transmittance of a thin layer of a magnetic fluid with Fe2O3 nanoparticles and transformer oil ITO 100 as base fluid, as a function of its thickness. Thin layer samples of the magnetic fluid with various thicknesses were prepared using standard microscope glass slides and spacers with defined thicknesses ranging from 25 µm to 530 µm. The stable spatial localization of the thin layer was ensured due to the existence of a surface tension emerging at the interface between the magnetic fluid surface and surfaces of the microscope glass slides. The transmittance as a function of the layer thickness was investigated in visible (VIS) and near-infrared (NIR) spectral ranges and spectral dependence of the coefficient of absorption of the magnetic fluid was determined, too. At the same time, the change of color of the layers depending on their thicknesses was evidenced. The results show the transmittance dependence on the thin layer thickness can be used to design magnetic fluid-based passive optical attenuators and filters.