Study On The Transmission Characteristics Of Spin Waves In Coupling Structure

Integrated circuits based on CMOS technology are restricted by physical size limits and power dissipation,which is difficult to achieve further scaling development.Moreover,the in-depth research on machine learning and neural network calculations makes it difficult for the Boolean operations provided by traditional transistors to meet the requirements.The unique advantages of spin and spin-wave devices in high-speed,low-power,non-Boolean operations and other fields make them be a strong candidate for new devices and are favored by researchers at home and abroad.In recent years,magnon circuits based on magnon(the quantum state of spin waves)calculations have attracted the attention of researchers due to the ability to make up for the bottleneck problems encountered in CMOS circuit technology.However,we cannot effectively distribute the power of the spin wave in the"X"-shaped or"Y"-shaped cross wiring structure because of the special anisotropy of the spin wave propagation.It is necessary to use the coupled spin wave device to connect Each independent controllable functional module in the spin wave circuit,hence,the study on coupled spin wave devices is particularly important.Based on the analysis of the current research progress of spin-wave coupling structures in domestic and overseas,this thesis proposes a corresponding solution to the problem of low spin-wave coupling efficiency that to reduce the coupling length of the spin wave in the waveguides by coupling yttrium iron garnet(YIG)and CoFeB magnetic material.Firstly,the compilation of the spin wave waveform analysis software package in the micromagnetism simulation is completed in this thesis,and then we use the compiled software package combined with the micromagnetism simulation and theoretical analysis methods to study the propagation of the spin wave in the magnetic coupling structure of different materials.After that,a method of using CoFeB material to modulate the transmission characteristics of the YIG spin wave waveguide is proposed;finally,the propagation characteristics of the spin wave in the coupling structure are analyzed in detail,and its internal mechanism is explained at the same time.The following study results and conclusions are mainly obtained:(1)The spin wave waveform analysis software package used in the post-processing of data in the micro-magnetism simulation has been written,which can be adapted to micro-magnetism simulation software such as MUMAX³.The batch processing of simulation data can be realized,which provide an effective solution for the completeness of the micro-magnetism simulation software tool chain.(2)It is found that the wavelength in YIG can be effectively modulated by the size of CoFeB in the YIG-CoFeB coupling mechanism,where the results can be used in spin wave phase shifters.In addition,the"sandwich"structure of CoFeB/YIG/CoFeB can prevent the propagation of spin waves.Through Fast Fourier Transform(FFT)analysis,the transmission efficiency of spin waves is the highest at 16.35 GHz has been found.The propagation of the spin wave at the remaining frequencies is almost completely blocked,and the frequency value is extremely sensitive to the magnetic field.(3)Spin-wave directional coupler structure based on YIG and CoFeB coupling is proposed.Investigation shows that compare with the traditional single-material directional coupler,the coupling length can be shortened to 1/4 of the original.At the same time,the uneven internal effective field distribution in the waveguide changes the propagation state of the spin wave in the waveguide.The analysis shows that the change of the coupling length comes from the dipole coupling mainly.Through the performance comparison of the directional couplers under different sizes,the coupling between the waveguides and the coupling inside the waveguides are analyzed,and the coupling in the dual waveguide coupling mode is proposed.The relationship between the length and the coupling strength inside the waveguide and between the waveguides is proposed:L=L₀×(I_in/I_between),where I_in is the spin wave coupling strength inside the waveguide,I_betweenis the coupling strength between the waveguides,and L₀ is the general coupling length.(4)It is found that the filling of the magnetic material in the waveguide gap layer of the YIG waveguide-based spin wave directional coupler can shorten the coupling length by several times in a certain frequency range(approximately 2.5 GHz-5 GHz),and spin wave inside can propagate About 180ns effectively.Finally,a structure for effective spin wave injection is proposed,which can be used to replace the decoupling structure in general directional couplers.