Figure 4.

(A,B) Experimentally measured transmission of the cobalt based ferrofluid at λ = 1.55 μm as a function of cobalt concentration, external magnetic field and polarization angle. As shown in panel (B), in the absence of phase separation polarization curves exhibit the Malus law sin²ϕ dependencies. On the other hand, in the phase separated state polarization curves exhibit universal “polarization notch” behaviour indicating long range order of periodically aligned cobalt nanocolumns. (C) Experimentally measured transmission of the ferrofluid at α(∞) = 8.2%, λ = 488 nm and B = 1630 G. (D) Polarization contrast measurements (data points) in the 0.5–10.6 μm range provide experimental validation of Maxwell-Garnett approximation (red line) at low nanoparticle concentrations. (E) Visible and near IR light propagation through a stratified ferrofluid. Due to much higher absorption in the cobalt rich phase, ferrofluid may be represented as multiple Fabry-Perot - like resonators separated by strongly absorptive regions of cobalt rich phase. (F) Calculated transmission of such a model stratified ferrofluid at λ = 1.55 μm.