Induced optical anisotropy by nanomagnetic particles in nanofluids

Magnetically induced extinction of light for two orthogonal states of polarization by nanomagnetic particles (magnetite) in an aqueous nanomagnetic fluid is studied. It is observed that nanomagnetic particles in such fluids exhibits field-induced optical anisotropy when subjected to an external magnetic field and obeys Rayleigh dipolar scattering theory. Using a theoretical model, particle size and surfactant layer thickness is obtained. Results are compared with magnetic birefringence and small-angle neutron scattering (SANS) techniques. This technique can also detect small aggregations in such nanofluids. It is proposed that the magnetically induced light extinction technique is a very much comparable and low cost technique for colloidal nanomagnetic fluids (ferrofluids).