Measurement of Birefringence and Dichroism in Magnetic Fluid Doped with Silica Microsphere

We used the Stokes polarimeter for measuring the magnetically linear birefringence and dichroism in composite magnetic fluids (CMFs). CMFs were prepared by doping nonmagnetic microspheres into pure magnetite ( Fe₃O₄) MFs. Experimental results show pure Fe₃O₄ MFs of different volume particle concentrations and CMFs doped with silica microspheres of equal quantity have similar variation trends for retardance and dichroism under magnetic field. The relation between birefringence and dichroism of CMFs doped with silica microspheres of different concentrations and those of pure Fe₃O₄ MF were investigated. It is found that the suppression of both retardance and dichroism increases with the increasing concentrations of silica microspheres in CMFs.