Linear birefringence and dichroism measurement in oil-based Fe3O4 magnetic nanoparticles

► Dispersed Fe3O4 magnetic nanoparticles (MNPs) are produced by a co-precipitation method. ► Simultaneous ultrasonic vibration and mechanical stirring are used in titration and coating. ► Diameters of Fe3O4 MNPs are determined as 11 nm with maximum magnetization as 54.27 emu/g. ► Birefringence and dichroism of ferrofluids are obtained by a Stokes polarimeter successfully.