Magnetic quenching of photonic activity in Fe₃O₄-elastomer composite

We report a quenching phenomenon within the visible region of the electromagnetic spectrum in the photonic response of a passive Fe₃O₄-silicone elastomer composite film due to magnetically aligned Fe₃O₄ nanoparticles. We performed systematic studies of the polarization dependence, the effect of particle size, and an in- and out-of-plane particle alignment on the optical response of the Fe₃O₄-silicone elastomer composites using a UV/vis/NIR spectrometer. We observed systematic redshifts in the response of the out-of-plane composite films with increasing particle alignment and weight that are attributed to dipole-induced effects. There were no observable shifts in the spectra of the in-plane films, suggesting the orientation of the magnetic dipole and the induced electric dipole play a crucial role in the optical response. A dramatic suppression to near quenching of the photonic response occurred in films containing moderate concentrations of the aligned nanoparticles. This is attributed to the interplay between the intra- and the interparticle dipoles. This occurred even when low magnetic fields were used during the curing process, suggesting that particle alignment and particle size limitation are critical in the manipulation of the photonic properties. A dipole approximation model is used to explain the quenching phenomenon. An active system of such a composite has a potential application in magneto-optic switches.