Polarization dependent extinction coefficients of superparamagnetic colloids in transverse and longitudinal configurations of magnetic field

• Scattering theory for diluted ferrofluids is described.
• The theory is extended for mixture of ferrofluids and magnetic suspensions of microspheres.
• Contribution of magnetic holes is discussed.
• Polarization dependent extinction coefficients in each case are derived.
• Advantages of measurements of polarization dependent extinction are discussed.

We review here, our work on the light scattering by ferrofluids and mixture of ferrofluids and other nonmagnetic suspensions subjected to an external static magnetic field. Detailed derivation of extinction coefficients of the systems when incident light is propagating along transverse and longitudinal direction of the field are carried out. In case of inclusion of anisotropic diamagnetic micron sized particles in a ferrofluids, effects of‘magnetic holes’ generated in the system on the extinction are discussed. The present work is analyzed in light of other similar investigations. It is shown that the study of polarization dependence of extinction coefficients in transverse field configuration is useful to arrive at an unambiguous conclusion regarding chain formation in a ferrofluid.