Research Of Spintronic Devices Based On Ferromagnetic And Antiferromagnetic Materials

After the discovery of giant magnetoresistance effect?GMR?,spintronics emerged from magnetic physics as an independent part due to its widespread application in the field of information encoding,transmission and processing.Spintronics injected new ideas into the design of electronic devices,thus the concept of spintronic devices was occurred.Unlike traditional electronic devices,which focus on the charge of electrons,spintronic devices realize their functions by modifying the spin of electrons.Compared with magnetic field or spin polarization current,regulating spin by electric field is more efficient and energy saving.Therefore,the effective regulation of magnetism by electric field has been a goal in spintronic field.Majority of research in this area focuses on multiferroic materials.The exploration of materials is important in design and preparation of new spintronic devices.So far,spintronic devices are mainly composed of ferromagnetic materials,like magnetic tunneling junction and spin valve,which have been widely used in data storage field.For regulation of magnetism by electric field,great progress has been made in ferromagnetic materials.Coercive filed and Curie temperature has been successfully modified by electric field.But when it comes to the most crucial branch,i.e.electric control of magnetic moment directly,only several works have been reported.Antiferromagnetic materials have several advantages over ferromagnetic materials.Antiferromagnetic materials have zero magnetization or low magnetization,insensitive to external magnetic fields.The intrinsic frequency and the frequency of the transition between different states of the antiferromagnetic material is several orders of magnitude higher than that of a typical ferromagnetic material.And antiferromagnetic ordering in semiconductors can be observed under softer conditions than ferromagnetic ordering.These advantages make antiferromagnetic materials very attractive in spintronics.However,the regulation of magnetic moment in antiferromagnetic materials is still a great challenge currently.In addition,two-dimensional?2D?magnetic materials have good application prospects in spintronics due to their stable storage,faster response,and low power consumption.These materials have important research significance in both areas of basic research and spintronics applications.Only few 2D magnetic materials have been found so far,and research of their magnetoelectric properties is little,further exploration is urgently needed.In conclusion,spintronic devices based on ferromagnetic materials,antiferromagnetic materials and 2D magnetic materials all have widely application,but also many challenges.Therefore,this article studies spintronic devices from the following three aspects:designing and preparing magnetic spin-capacitors based on ferromagnetic materials,studying the manipulating of anti-ferromagnetic magnetism,and preparing and studying the magnetoelectric properties of two-dimensional magnetic materials.The following research is carried out in the design and preparation of spintronic devices:1.An electronically controlled magnetic device with column structure was designed.In order to realize the device preparation,a 3D direct write device was independently built.The spin capacitor device with a column structure was successfully prepared and tested for magnetic properties.Although it can be seen that electric field has influence on the electric density,due to the special features of the structure,the device is easily broken down and hard for magnetic measurement,thus repeatability and reliability of the device is rather low.2.Based on the column spin capacitor device,a cylindrical coaxial structure spin capacitor based on Cu/Ni was designed.A coaxial cylindrical structure was used instead of the column structure and the ion-gel technology replaced the traditional insulation layer.Compared with the traditional layered structure,the specific surface area was greatly increased;more importantly,the ion-gel technology made the effective electric field very large.The improved spin capacitor showed excellent performance.At room temperature,only 2 V voltage can increase the saturation magnetic moment of the device by 18%.In addition,the application of this structure to metal ferro-platinum?FePt?will further improve device performance.3.The Co/IrMn heterojunction was designed to verify whether antiferromagnetic magnetic moment can be controlled at room temperature by the interaction of ferromagnetic and antiferromagnetic double layers.We conducted a test of magnetoresistance change with magnetic field and with the direction of the magnetic field on Co single layer and Co/IrMn double layer.It has been observed that the magnetoresistance of Co/IrMn double layer increases by an order of magnitude compared with that of a Co single layer,control of antiferromagnetic moment at room temperature was successfully achieved.And the exchange bias of the device was also studied,large exchange bias was found in perpendicular direction.4.Single-layer and few-layered vanadium selenide were prepared.A series of optical and electrical properties were characterized.When the thickness down to single layer,it was converted into semiconductor.Raman spectra of vanadium selenide films were studied,and the law of the shift of Raman spectra with film thickness were summarized.5.A large size,continuous and uniform 2D magnetic material CGT was attempted to be prepared by magnetron sputtering.Different substrate temperatures were applied to fabricate the film.It was found that the as grown films were mixture of CrTe and GeTe,not CGT.Then we tried to anneal it and obtained a mixture film of CGT,Cr₂Te₃ and Cr.