Fabrication And Transport Measurement Of Micro-Nano Devices Of Two-dimensional Ferromagnetic Material Fe₃GeTe₂

In recent years,the discovery of two-dimensional ferromagnetic materials provids a new direction for the research and development of spintronic devices.Among them,the Fe₃Ge Te₂ is a typical metallic ferromagnetic two-dimensional material with a Curie temperature of～220K and strong perpendicular magnetic anisotropy.Although it has the characteristic that the Curie temperature becomes lower as the thickness becomes thinner,the Curie temperature of Fe₃Ge Te₂ can be raised to above room temperature through ion gate control.This maneuverability makes it have the potential to be applied to various spintronic devices like traditional metal ferromagnetic films.The research on the physical properties of Fe₃Ge Te₂ and its integration into spintronic devices is still in the preliminary stage.This dissertation focuses on the physical properties of the two-dimensional ferromagnetic material Fe₃Ge Te₂ in device preparation,optical characterization and magnetoelectric transport,and hope to expand its application in spintronic devices.The main research contents are as follows:（1）X-ray diffraction and energy dispersive X-ray spectroscopy are used to determine the composition quality of Fe₃Ge Te₂ single crystal to ensure that it can conform with our experimental requirements.Prepare Fe₃Ge Te₂ nano-scale flakes of various thicknesses,test the Raman spectrum and study the different vibration modes of Fe₃Ge Te₂ nano-scale flakes under Raman light.According to the experimental results,it is found that the characteristic peaks were depend on the thickness.This trend may establish correlation between the characteristic peaks of the Raman spectrum and the thickness of Fe₃Ge Te₂.（2）By preparing uniform thickness-Fe₃Ge Te₂ devices and studying its low-temperature transport properties,it is determined by abnormal Hall resistance measurement that it has low-temperature ferromagnetism and its Curie temperature is～190K,rectangular hysteresis loop and as the temperature rises,the coercive force becomes smaller and the area of the magnetic ring becomes smaller,changing from hard magnetism to soft magnetism.The magnetoresistance curve appears as a butterfly curve of conventional ferromagnetic metals.（3）In the non-uniform thickness-Fe₃Ge Te₂ device,the anomalous Hall curve is different from the uniform thickness-Fe₃Ge Te₂ device in that the state of multiple magnetic phases appears in the magnetization switching stage,which indicates that there are multiple magnetic domains in the magnetization switching stage,and the Curie temperature is～180K.In the magneto-resistance result,antisymmetric peak was observed during the magnetization switching stage.The analysis believes that this antisymmetric magneto-resistance phenomenon comes from the non-uniform thickness-Fe₃Ge Te₂,which causes the magnetization of different thicknesses-Fe₃Ge Te₂ to reverse successively during the magnetization switching process.As a result,boundaries appear at the junction of different magnetized regions,and the current density in the device is interfered by circulating currents near the boundaries,resulting in the appearance of antisymmetric magnetoresistance.