Suspensions of nickel nanowires as magneto-optical switches

Application of modest magnetic fields can be used to control the direction in which laser light incident on aqueous suspensions of magnetic Ni nanowires (∼200 nm in diameter and ∼10 µ mi n length) is preferentially scattered. Similar effects were observed for suspensions of these nanowires prepared in ethanol, ethylene glycol, and glycerol. In glycerol, the nanowires settle sufficiently slowly that the effects can be quantified. In particular, fields of the order of 100 Oe cause the intensity of light scattered in the forward direction to vary by as much as a factor of thirty-five simply by changing the direction of the field.