Study Of Spin Current Transport And The Dynamic Properties In Magnon Valve

Computers and electronic equipment are now in the era of high-speed iteration,thanks to advances in science and technology.There is a pressing need to produce smallersized transistor units to boost computer computation speed and storage density even more.Now,the transistor has entered the 7 nm process technology,and the bottleneck of the atomic limit and quantum effects are increasingly apparent.Keeping the current generation of processes going is considerably more difficult.Spin has emerged as a novel way to get through this bottleneck in recent years.Spintronic devices are represented by magnetic insulators,which can carry out long-distance and efficient information transfer in the form of the spin angular momentum with the assistance of magnons,and the device's power consumption is greatly decreased without net charge movement.As a result,the creation of spintronic devices based on the magnon valve,in order to realize logic,storage,and a variety of devices with magnon spin,has gotten a lot of interest.To further enhance this sort of device,this thesis uses the magnon valve insulator heterojunction as the basic unit and explores its potential for new applications,concentrating primarily on two directions: Firstly,the performance of the magnon valve is systematically studied.Through the asymmetric breakage of its structure,the magnon valve magnetic dynamics and Fano resonance are combined to realize the Fano effect of the magnon valve.Then,the transfer of spin information mediated by phonons was realized by combining with the interaction between magnons and phonons,and the spin transport properties of a YIG/GGG heterojunction were studied by combining the test methods such as spin pumping,spin Hall,and inverse spin Hall.This is of great significance for realizing spin current transmission and detection based on magnon and developing high-performance spintronic devices.First of all,this thesis introduces the existing related theories and backgrounds.Based on the theory of magnetic dynamics,the precession process of magnetization is analyzed from the perspective of magnetic energy.The theoretical models and applications related to ferromagnetic resonance and Fano resonance,spin current generation and detection mechanism,provide a theoretical basis for the subsequent studies on the spin transport and dynamics of the magnon valve structure.The sample preparation and testing techniques used in this thesis are also introduced.Secondly,the preparation process and method of the new magnon valve structure YIG/Au/YIG are studied.Specifically,different structural types of magnon valve units were obtained by changing the thickness of the Au layer,including YIG/Au nanoparticles/YIG,YIG/Au nanorods/YIG,etc.Different types of magnon valve units are characterized by TEM,XRD,Raman,XPS.The microstructure model of the magnon valve and crystal structure,phonon vibration mode,and element valence are analyzed and discussed in detail.The optical properties of the YIG/Au/YIG magnon valve are studied by UV-visible test,and the change of its optical band gap is calculated by its transmission spectrum and reflection spectrum.It is found that with the increase of the thickness of the Au layer,the optical band gap gradually decreases.Thirdly,the magnetic properties of the YIG/Au/YIG magnon valve with different thicknesses of the Au layer are systematically studied,and the magnon Fano resonance phenomenon is successfully observed in the magnon valve with an Au layer of 60 nm.Specifically,through the coupled oscillator model,the source of the Fano resonance is described,and the Fano factor is extracted by numerical fitting to the ferromagnetic resonance absorption peak.It is found that the Fano factor can define the direction of the interaction between the ferromagnetic layers.Finally,to further explore the magnon spin devices based on pure spin currents,YIG/GGG/Pt heterojunction are prepared,and related studies on spin transport are carried out.The GGG film obtained by pulsed laser deposition presents a polycrystalline thin film dominated by the(111)crystallographic orientation,has Raman peaks corresponding to different structures.On this basis,the inverse spin Hall effect under the condition of GGG spacer layers with different thicknesses is studied to explore the possibility of phonon spin transport.In the YIG/GGG/Pt heterojunction,the inverse spin Hall signal within 100 nm of the GGG layer is successfully detected by the inverse spin Hall test system.Spin transport decays exponentially within 100 nm with the increase of GGG film thickness.