The Construction Of Functional Oxides And Its Application In Co-based Spintronic Devices

In recent years,with the practical application of spintronics devices in the field of information storage,the structure and regulation of spintronics devices have attracted more and more attention from the scientific community.As an important control method,the oxide insertion layer plays an important role in the regulation of the electrical transport and perpendicular magnetic anisotropy of spintronic devices.Therefore,it is necessary to find effective,stable and feasible spintronic devices.The oxygen ion source with reversible input and output has become the focus of research.At present,the main ways that academia can control the magnetism of spintronics include:1)Using the stress generated by the piezoelectric properties of piezoelectric materials,using the electric field to control the stress to adjust the magnetic perpendicular anisotropy;2)Using ultra-thin The oxide is used as the substrate layer or cover layer to adjust the magnetic properties of the device;3)Using electric field to adjust the chemical properties of the interface to adjust ferromagnetism.Through these methods,scientists succeeded in realizing the regulation of the properties of spintronic devices,which played an important role in promoting the development of spintronics.Although it has been achieved partly based on the electric field to regulate the magnetic properties of spintronic devices,the amplitude and reversibility of the regulation still need to be further improved.Many new physical phenomena have yet to be discovered,and the underlying physical mechanisms have yet to be clarified.Therefore,this dissertation focuses on electric field control based on oxide intercalation,adopting three methods:amorphous oxide intercalation,epitaxial lattice stress,and electric field control interface oxygen ion concentration.The important physical effects in spintronic devices such as spin orbital moments are regulated and studied,and the physical nature of oxide intercalation regulating spintronic devices is explored.(1)Use amorphous CaTiO3 and BaTiO3 as intercalation layers to adjust the magnetic perpendicular anisotropy of the Co layer in the heterojunction CaTiO3/Co/Pt and BaTiO3/Co/Pt layers.A large number of experiments have been carried out on the growth conditions of CaTiO3 and BaTiO3,the growth process has been optimized,and an ultra-thin(about 5nm)amorphous oxide layer has been inserted to use the oxygen ion of the oxide layer to hybridize with the Co orbital to enhance Co layer perpendicular magnetic anisotropy.Among them,for the sample with amorphous CaTiO3(5nm)inserted,compared with the SrTiO3 substrate one,at a temperature of 50K,the vertical anisotropy of can be increased by 7 times,and the coercive field can be increased by about 150Oe.And this method is used to enhance the perpendicular magnetic anisotropy of the Co layer on other functional oxides.(2)Using the ferroelectric material PbTiO3 to control the electric field of the magnetization reversal process of the magnetic multilayer film induced by the spinorbit torque in the Co/Pt bilayer film.The PbTiO3/Co/Pt Holbar device with critical perpendicular magnetic anisotropy was fabricated on SrTiO3 on the perovskite substrate.An electric field perpendicular to the surface of the film is applied to PbTiO3,and oxygen ion migration generated by the polarization electric field of PbTiO3 is used to realize the reversible control of the magnetization reversal field,magnetic domain wall motion and current-driven magnetization reversal process of the Hallbar device.By controlling the polarization direction of the electric field at the input end,we can control the size of the coercive field at the output end,and the coercive field of the device can be adjusted in the range of 550-750Oe at a temperature of 50k.(3)We achieved the growth of super tetragonal PbTiO3 thin film through the modulation of growth conditions.The c-axis(perpendicular to the surface of the film)lattice parameter of the PbTiO3 film is as high as 4.71 A and the c/a ratio is 1.2.And the specific structure coefficient can be customized by adjusting the growth conditions(such as the temperature and oxygen pressure during growth).In addition,the microstructure of the super tetragonal body was characterized,and it was found that the structure was a self-assembled nano-column structure,which was formed by splicing the lead excess phase and the PbTiO3 super tetragonal phase.Each square PbTiO3 area was at the nanometer level and uniformly dispersed.With the structure coefficient c/a=1.2 of the organization,we estimated the polarization of the structure to be approximately 177 ?C cm-2.This work provides the possibility to design spin logic devices controlled by nonvolatile ferroelectric thin films,which spontaneously form self-assembled nanostructures without being restricted by single crystal substrates.We also emphasize that this method can be widely applied to the growth of other microelectronic oxide materials to expand oxide lattices with emerging functions to regulate spintronic devices.