Thermodiffusion study in ferrofluids through collinear mirage effect

We studied some thermodiffusion effects for ferrofluid samples with two different kinds of surfactant by mirage effect technique. We focused a laser beam in the sample introducing a heat gradient that provoked ferroparticles mobility (thermodiffusion) and analyzed the behavior of the mirage signal as a function of the pump laser beam intensity, for a fixed frequency. The main results showed that for the ferrofluid with anionic surfactant no thermodiffusion variation was verified, even for the most concentrated sample. On the other hand, for the cationic one we observed an increase in the thermodiffusion with greater ferroparticles concentration. Therefore, we showed that collinear mirage effect technique can be used for detecting Soret effect generated by the thermal interactions between the laser radiation and the highly absorbing material.