Spectral and magnetic field dependence of the birefringence of a magnetic fluid

Abstract

The paper presents the result of an experimental investigation of the effect of a magnetic field on the transmittance of a magnetic fluid placed between two crossed linear polarizers and illuminated by light from a supercontinuum light source. The change of the optical signal in the visible region detected behind the output polarizer depending on the magnetic flux density shows that the magnetic fluid becomes optically anisotropic, and the change of the optical signal is the consequence of the so-called birefringence induced by a magnetic field oriented perpendicular to the direction of the light beam passing the magnetic fluid sample. The phenomenon was observed on samples of magnetic fluid with Fe₃O₄nanoparticles dispersed in ITO100 oil and thicknesses from 25μm to 380μm in static fields with values of magnetic flux density up to 60mT. The dependence of birefringence on wavelength, magnetic flux density, and sample thickness is evident from the measured dependencies.