Fabrication Of Y₃Fe₅O₁₂and Pure Spin Current Spin Valve Based On Its Single Crystal Film

Electrons have two properties:electronic charge and spin.In the past few decades,traditional microelectronics based on the properties of electronic charge has flourished.However,it has the problems,such as high power consumption and low integration.To solve these problems,people turned their attention to another property of electrons,namely spin.Since the discovery of the giant magnetoresistance(GMR)effect in magnetic multilayer films in 1988,a new branch of physics and technology based on the spin properties of electrons has appeared,called spin-electonics or spintronics.Compared with traditional semiconductor devices,increasing spin freedom or using spin alone in charge-based electronic devices adds many advantages:non-volatile,increased data processing speed,reduced power consumption and increased integration density.In spintronics,the spin of electron is manipulated and controlled along with the charge.In order to introduce spin into semiconductor technology based on electronic charge,the effective injection,transfer,control,manipulation,and detection of spin currents are still important.In recent experiments,researchers usually use some effects to inject spin current,such as spin Hall effect,spin pumping effect,photoexcitation,spin Seebeck effect,etc.Among all ferromagnetic materials used in the experiment of injecting spin current,Y3FesO12(YIG)as a ferrimagnetic insulator material,due to its small damping,good electrical insulation properties,high Curie temperature,high chemical stability can greatly reduce the energy consumption of electronic device,so it has great potential.Regarding the detection of spin currents,researchers usually use non-magnetic heavy metals(such as Pt,W,Ta etc.)to convert spin current to charge current which can be detected through the inverse spin Hall effect.One of the work of this thesis is the fabrication of yttrium iron garnet ferromagnetic insulator target and its single crystal thin film.In the process of sintering the target,we chose the nitric acid fusion sintering method.Because comparing with the traditional solid phase reaction method,this method allows raw material Y2O3,Fe2O3 to be fully mixed during the sintering process,which improves the purity of the target After pre-sintering,high-temperature sintering,the high-purity two-inch YIG cylindrical target was successfully fired.We used XRD diffraction and AGM to test the microstructure and magnetic properties of the target powder.On this basis,we used self-sintered targets to grow YIG films on GGG substrates by magnetron sputtering technology and characterized the grown films by AGM,XRD,and ferromagnetic resonance measurement systems.Another work in this paper is to observe the ferroic non-collinear spin valve effect based on pure spin current in the magnetic multilayer structure of YIG/Pt/NiFe/IrMn.In this structure,the voltage amplitude measured by ISHE depends on the magnetization state(saturated or unsaturated)of the NiFe layer,which yields a spin valve-like behavior.We believe that this effect is due to the different spin transparency of the Pt/NiFe interface caused by different magnetization states of the NiFe layer.We observe the relative change in voltage amplitude is up to 120%.We demonstrate the reliability and stability of this spin-valve effect and determined its origin.We finally provide a non-collinear spin valve based on pure spin current.