Propagating Characteristics And Manipulation Of Spin Waves In The Yttrium Iron Garnet Micro-Stripes

Spin waves are the collective excitation of magnetic moments in magnetically ordered materials.The application of spin waves for data transmission and processing takes the advantages of low power comsuptions and high efficiencies,and has gradually become the hot topic in recent years.With the decreasing feature size of the mordern microfabrication techniques,many novel spin wave functions can be realized through the microstripe waveguide.Therefore,the characteristic and the manipulation of spin waves in microstripes are critical toward the engineering application.Among various magnetic materials,yttrium iron garnet(Y3Fe5O12:YIG)is widely used for the study of the transmission characteristics of spin waves due to its small damping coefficient.Its effective magnetic field is also easy to be tuned by the external magnetic field because of its low saturation magnetization and magnetocrystalline anisotropy.Under such backgrounds,the propagating characteristics and manipulation methods of spin waves in YIG microstrip waveguide,which is magnetized by lateral and proximate permalloy(Ni81Fe19:Py)microstructures are studied in this dissertation.It lays a solid theoretical foundation and practical application for the realization of related device functions in the future.The research contents of this dissertation include:(1)YIG and Py films were prepared by magnetron sputtering respectively.The damping coefficient,saturation magnetization and ferromangetic resonance line width of YIG and Py films were characterized by using the microwave ferromagnetic resonance method.They are the basis for the subsequent research on the transmission of spin wave in YIG microstrip waveguide.The corresponding patterned film was designed and prepared,and the Brillouin light scattering experiment was used to verify the spin wave transmission characteristics and the manipulation based on theoretical analysis and simulation research.(2)We proposed the model that the YIG microstripe was magnetized by the lateral and proximate Py stripe.We found that the dispersion curve of edge localized spin waves was split into two branches with the presence of Py microstrip.Using the continuous exctiation,the wavelengths,group velocities and attenuation lengths of the edge mode spin wave on both sides of the YIG microstrip waveguide were calculated.We further explored the reasons for the splitting of the dispersion curve,and analyzed the effect of the inhomogeneous static dipole field induced by Py microstrip in the width direction.This research provides a new idea for the design of the novel logic element based on spin wave interference.(3)We studied the interference between the odd and even modes of spin waves in YIG microstrip waveguide,as well as the physical mechanism and methods of manipulating this interference.Analytically,by changing the phase difference between the odd and even modes,the propagating patterns of the spin waves can be changed.We explored the methods to control the phase difference:through micromagnetic simulation,we demonstrated the phase difference is decided by the relative positions of the lateral Py dot;through microfabrication and brillouin light scattering experiments,we demonstrated the phase difference is determined by the external magnetic field.This research is helpful to the design of new devices in magnonic engineering.(4)Through micromagnetic simulation and Brillouin light scattering experiment,we studied the propagating characteristics of waveguide spin waves in the YIG microstripe waveguide with a lateral and proximate Py microstrip.The positions of propagating spin wave channels at different frequencies were studied under the fixed external magnetic field.The variation of the position of the transmission channel of the fixed frequency spin wave was also studied with the various external fields.Based on these studies,we explored the implementation of the spin waves frequency division multiplexing function.These studies help to achieve parallel transmission and processing of spin wave information in magnonic engineering.