A Study On The Application Of Surface Plasmon In Spintronic Device

Surface Plasmon is a surface mode due to the interaction of metal and electromagnetic wave, existing in the interface between metal and dielectric. It’s the collective oscillation of masses of free electrons in metal as a response to electromagnetic wave. These modes can be divided into two types:propagating surface plasmon (PSP) and localized surface plasmon (LSP). Both modes could bind the eletromagnetic wave on the interface and make the electromagnetic field in the near-field region enhanced by several orders respective to the incident field. The enhanced field could be applied in many fields, such as Surface Enhanced Raman Spectroscopy, Enhanced Optical Transmission, Enhanced Quantum Well Infrared Photodetector and so on.Electric detection of ferromagnetic resonance is a powerful experimental tool. Over the past ten years, this technique has attracted many researchers in the communities of magnetism, spintronics, and microwave technologies. It has been broadly used for studying diverse material structures, such as ferromagnetic thin films, bilayer devices, magnetic tunneling junctions (MTJ) based on magnetic multilayers and so on. Spin rectification is an important electric detection tool of spin dynamics, which is one of the significant effects in the system of ferromagnetic thin film. The DC voltage generated by the spin rectification is proportional to the product of microwave electric and magnetic field components. It has potential applications in microwave detector, nondestructive detection, dielectric measurement and so on.The two fields depicted above are the active areas in the current academe. But there are few works about the discipline of Plasmonics and Spintronics. Based on the abounding physical phenomena and potential application of the two fields, it’s significant both in theory and application to study the discipline of Plasmonics and Spintronics.In this thesis, a novel Plasmonic Antenna (PA) is designed, which could be considered as two back-to-back Split Ring resonators (a type of fundamental element of metamaterial). This PA is like the LC circuit and has its intrinsic resonant frequency which is determined by its dimension. At the resonant frequency, the PA can largely enhance both the electric and magnetic components of electromagnetic wave in its near-field region. This character satisfies the need of spin rectification, and of course, the PA could be designed to match many different demands, which is one of its advantages. In the experiment, the PA is used to harvest microwave energy to assist the spin rectification to generate an enhanced DC voltage, and the enhancement could reach two orders more. Though, this enhancement is smaller than the calculated one using FDTD method (enhanced by three orders), it’s enough to demonstrate the powerful ability of PA. Based on the PA, a Plasmonic cavity is designed to enhance the DC voltage generated by spin rectification, consequently, the enhancement could reach three orders more.