Investigation of polarization magnetooptic responses of a low-concentration ferrofluid

A highly sensitive laser polarization-optical technique was developed and applied to investigations of a ferrofluid, which was placed in a magnetic field. A colloid solution of magnetite in kerosene was used as a sample. It was shown that the magnetooptic response of this substance is reliably registered at a volume solid-phase content of down to $\sim$10$^{-5}$. It was revealed that within a very wide range of changes in the solution concentration, a quadratic dependence of the observed birefringence value on the low-intensity field (up to several tens of oersted) is retained.