Nanowire light scattering variation induced by magnetic alignment

We report the preparation of Ni nanowire colloidal suspension that exhibits large light scattering changes when a magnetic field is applied. These changes occur during the application of alternating transversal magnetic fields. The intensity variation can easily be detected and measured since the light signal produced is very large with ratios much larger compared with signals obtained from light transmission through the nanowire colloidal suspension. Ni nanowires used for the experiments are about 1.2 μm long and 50 nm in diameter; suspensions of 44 μg/ml of these nanowires yield a scattering light variation ratio up to 35% when subjected to transversal alternating magnetic fields of 10 G. The methodology proposed could be implemented to detect and characterize magnetic nanowires even at concentrations as low as 4.4 μg/ml. Using finite element modeling, we observe that nanowires in a suspension scatter light depending strongly on the incidence angle of the applied light. From the finite element simulations, we also observe that nanowires may present plasmonic-antenna absorption effects that can be useful to indirectly measure nanowire properties, such as length and composition.