Preparation And Properties Of Magnetic Heterostructure Based On Single Crystal Ruthenium Oxide

With the development of the information age,enormous amounts of data need to get processed and stored rapidly.Therefore,computers based on the traditional von Neumann architecture are severely challenged in terms of speed and energy consumption,and new computing paradigms such as brain-like computing and the integration of storage and computing have emerged.Among them,the third-generation magnetic random memory device based on the Spin Orbit Torque（SOT）effect,which features fast read and write speeds,and non-volatility,is one of the ideal memories for integrating storage and computing.The generation of SOTs depends on Spin Orbit Coupling（SOC）,so finding material systems with a large spin hall angle has become a focus of research in this field.In recent years,researchers have found that the anisotropic spin splitting effect（ASSE）is caused by anisotropic crystal fields and strong antiferromagnetic exchange coupling between magnetic atoms,and that ASSE is a novel method to generate spin flow independent of SOC.ASSE’s discovery thus broadens the selection of materials for the third generation of magnetic random access memory,and infuses new life into material systems capable of effectively generating spin flows.As determined by theoretical calculation and experimental corroboration,ASSE exists in the collinear antiferromagnet RuO₂,which can be used to generate pure spin flow under the influence of an applied electric field.ASSE comes from its special anisotropic spin splitting band structure.Therefore,ASSE can be used to generate spin flows,namely,only RuO₂with specific crystal orientation can produce spin flows that have effects on the neighboring ferromagnetic layer,so as to prepare the heterostructure of RuO₂/FM and study the spin injection of RuO₂into the neighboring ferromagnetic layer.We have carried out research in the following three areas:（1）Preparation of RuO₂thin films with good crystallinity and specific crystal orientation.RuO₂films were prepared by reactive sputtering of Ru target in oxygen environment using magnetron sputtering.Using reflected high-energy electron diffraction and X-ray diffraction as characterization methods,the experimental rules and precautions of epitaxial RuO₂on different single crystal substrates were summarized.（2）RuO₂/Fe Ni heterostructures were prepared based on RuO₂with different crystal orientations,and spin transfer moment ferromagnetic resonance testing was carried out.By comparing the difference of spin hall Angle between RuO₂（100）/Fe Ni and RuO₂（110）/Fe Ni thin films,it is proved that the extra spin contribution in RuO₂（100）comes from ASSE.（3）RuO₂/Fe Ni heterostructures with different thicknesses were prepared and tested by ferromagnetic resonance.The relationship between the damping of bilayer film and Fe Ni thickness is determined,and the spin-pumping effect exists in RuO₂（100）/Fe Ni.By comparing the damping of RuO₂with different orientations,it is found that the damping increment in RuO₂（100）is the reflection of ASSE inverse effect when RuO₂meets the laminar growth condition.