Form birefringence in ferrofluids

Measurements of the birefringence and dichroism, over the wavelength range 300-700 nm, in a Co and an Fe 3 O 4 ferrofluid are reported. The results for the Co fluid are interpreted in terms of a simple extension of the classical Wiener theory of form birefringence which takes into account absorption in the particles and in the carrier liquid. The results suggests that the optical properties of the fluid are due to aggregates of particles that occur at a relatively low density within the fluid.