Magneto-optical plasmonic Bi:YIG composite films with Ag and Au-Ag alloy particles

Abstract

To obtain enhancement and wavelength tuning of the magneto-optical (MO) response associated with the localized surface plasmon resonance (LSPR), bismuth-substituted yttrium iron garnet (Bi:YIG) composite films with Ag particles and Au-Ag alloy particles were studied. The Bi:YIG composite film with Ag particles did not show any enhancement of Faraday rotation. On the contrary, the Bi:YIG composite films with Au-Ag particles exhibited the enhancement of the MO response for different wavelengths of LSPR. We observed the enhanced Faraday rotation for the Bi:YIG/Au-Ag composite films with volume ratios of Ag up to 0.6. In addition, when changing the volume ratio of Ag, the peak of rotation shifted to short wavelengths. Disappearance of enhancement for the Bi:YIG/Ag composite film can be addressed to modifying the interfacial medium between the MO host and Ag. Since chemically active Ag particles can form nonmagnetic Ag compound shells separating Bi:YIG and the plasmonic subsystem, the LSPR of Ag particles did not affect the MO response. The Au-Ag alloy particles were chemically stable in the Bi:YIG/Au-Ag composite films.