Surface Plasmons And Magneto-optical Effects In Ag/Co Nanodot Arrays

During the last few decades,the surface plasmons have attracted a great deal of interests along with the progress of nanometer processing technology.Nanoparticles,represented by the precious metals of gold and silver,possess good surface plasmons properties.The optical properties are affected by many factors,such as nanoparticle size,nanoparticle shape and medium.Localized surface plasmon resonance has been investigated for biosensing,biological imaging,and photothermal therapy applications.Therefore,we can design a composite nanostructure consisted of metallic magnetic materials and noble metals.This structure possesses good surface plasmons property to make a relatively nice magneto-plasmonic crystal,thus the magneto-optical activity can be improved.Materials with increased magneto-optical activity could be used in the field of telecommunications,high density holographic data storage,3D displays and magnetic field sensing.So far,the magneto-optical activity has been studied in various systems,such as core-shell nanoparticles,nanodisks,nanowires,and so on.Actually,the studies are mainly focused on the properties of individual nanoparticles,which is random distribution with the subwavelength size to avoid the diffraction effect.Few people studied the effect of ordered nanodot arrays on magneto-optical activity.Anodic aluminum oxide template(AAO)is a well-known,low cost and feasible method for fabricating long-range highly ordered nanodot arrays.Therefore,this article uses the AAO template to prepare nanodot arrays which present magneto-optical activity.(1)Nanoparticle,obtained by the method of physical vapor deposition,is not restricted.In order to obtain the limited nanoparticle,the silver and cobalt nanodot arrays are respectively obtained by using AAO templates combined with magnetron sputtering.Through the limit of templates,we can get nanoparticles(nanodots)in the same size with good periodicity.The result shows that the absorptions are enhanced due to the exciting of localized surface plasmon resonance.Compared with magnetic transition metals of cobalt,the mental of silver present relatively good optical property.The absorption bands ofsilver have relative sharp and significantly symmetrical shape.Nevertheless,the absorptions of cobalt display a wide shape and poor intensity due to the high Ohmic losses.(2)We studied the morphologies,structures,magnetic properties,optical properties and magneto-optical activities of silver/cobalt dimer nanodot arrays by exploiting the same preparing method of single nanodot arrays.The results demonstrate the direct relationship between the optical properties and magneto-optical properties derived from the excitation of localized surface plasmon resonance,which make the electromagnetic field redistribution resulting in the enhancement of magneto-optical activity.