Y_(3)Fe_(5)O_(12)-CoFeB自旋波定向耦合器中的自旋波

Spin waves in Y_(3)Fe_(5)O_(12)-CoFeB spin-wave directional coupler

介绍了一种基于Y_(3)Fe_(5)O_(12)和CoFeB复合结构耦合的新型定向耦合器,并利用微磁学仿真软件Mumax^(3)及其配套工具链分析了自旋波在其中的传播特性.通过在Y_(3)Fe_(5)O_(12)定向耦合器中添加一种高饱和磁化强度材料(CoFeB)来增强耦合波导的耦合效率,并从器件的尺寸形状、内部等效场以及耦合机理等角度分析了其变化原因.结果表明,相较于传统的定向耦合器,这种复合结构能够极大地降低自旋波在耦合波导间的耦合长度.从应用的角度看,在功能相同的情况下,整个器件的长度可以缩短数倍,具有更好的发展前景.

The spin-wave coupling device is used as a connection unit to solve the connection problem between spin-wave devices.However,the current size is too large in comparison with the nano-scale process,which is caused by the low efficiency of the spin wave within it.Therefore,we propose the spin-wave directional coupler based on Y_(3)Fe_(5)O_(12)-CoFeB coupling which can improve the current dilemma to a certain extent.By filling the gap layer of two spin-wave waveguides(Y_(3)Fe_(5)O_(12))placed in parallel with CoFeB material,it is found that the dispersion relationship of the spin wave changes in the data calculation of the micromagnetic simulation software Mumax^(3).The existence of CoFeB makes the transmission efficiency of the spin wave between the two waveguides higher than in the case without any filling,the enhancement effect is about 4 times where coupling length is reduced from the original 2000 nm to 500 nm,which is conducive to the miniaturization and integration of the spin-wave directional coupler design.From the perspective of the entire device,further analysis indicates that owing to the high saturation magnetization of CoFeB(approximately 8 times that of Y_(3)Fe_(5)O_(12)),the effective field in the Y_(3)Fe_(5)O_(12)-CoFeB directional coupler is greatly enhanced,which leads the spin wave dispersion curve in the waveguide to change.At the same time,the energy of the entire system also increases several times,which is mainly caused by the increase of dipole energy and exchange energy.Then a greater contribution of dipole energy is obtained by changing the size of the device.After that,we study the relationship between the coupling length and the device size and the external magnetic field,then draw a general rule which can play a role in designing any directional couplers with similar structures.Finally,our view points are given from the different spin wave excitation frequencies,gap layer filling materials,internal roughness of the directional coupler,and spin wave lifetime by considering the problems that may occur in practical applications with the Y_(3)Fe_(5)O_(12)-CoFeB directional coupler.In conclusion,our proposed Y_(3)Fe_(5)O_(12)-CoFeB directional coupler structure can effectively enhance the coupling efficiency,and it can also provide a new idea for the application of the interaction between composite materials.