Magnetic Quenching of Plasmon-photonic Activities in Fe$_3$O$_4$-Elastomer Composite

We report for the first time, a systematic study of polarization dependence and the effect of particle size on the optical response of Fe$_{3}$O$_{4}$-silicone elastomer composites in the presence of external magnetic field. The optical response of composites containing 2wt{\%}, 5wt{\%} and 15wt{\%} of 20nm$\le $d $\le $30nm, 40 nm$\le $d$\le $ 60nm and d$\le $ 500nm Fe$_{\mathrm{3}}$O$_{\mathrm{4}}$ particles were aligned in- and out-of-plane in the elastomer host. We observed a systematic redshift in the optical response of the out-of-plane composite samples (containing nanoparticles 20nm$\le $d$\le $30nm) with increasing static magnetic field strength, which saturated near 600 Gauss. There were no observable shifts in the in-plane samples, suggesting that the orientation (polarization) of the magnetic dipole and the induced electric dipole play a crucial role in the optical response. However, we observed a dramatic suppression to near quenching of the plasmonic activities in the micron size particles (d \textless\ 500nm) elastomer composite, suggesting particle size limitations in modulation of plasmon-photonics by external magnetic field. Dipole approximation model is used to explain the quenching phenomenon.