Fabrication And Spin Transport Properties Of Magnetic Two-dimensional Fe₃GeTe₂ Heterostructures

In recent years,the emergence of intrinsic two-dimensional(2D)magnetic materials has broken the deadlock in the field of 2D spin electronics for many years,and provides a new platform for studying spin-related phenomena in van der Waals system.Compared to the 2D magnetic insulators CrI3 and Cr2Ge2Te6,Fe3GeTe2,as a novel 2D ferromagnetic metal material,has a higher Curie temperature and strong perpendicular magnetic anisotropy.More importantly,the Curie temperature of Fe3GeTe2 can be raised to room temperature and above by ionic liquid or changing the ion concentration,which provides the possibility to prepare spintronic devices with easy manipulation and ultra-high density based on this material and realize its application.At present,the research of spintronic devices based on the magnetic 2D material Fe3GeTe2 and its spin transport property is still at the exploratory stage.Therefore,this dissertation focuses on the preparation of the 2D magnetic Fe3GeTe2 van der Waals heterostructure and its spin transport properties.The main research contents are as follows:(1)Study on the spin transport characteristics of 2D magnetic Fe3GeTe2.The morphology and structure of Fe3GeTe2 were studied by means of structural characterization.The results showed that the materials were clean,flat,and free of impurities.The spin transport properties were studied by anomalous Hall tests,and the low-temperature ferromagnetism of Fe3GeTe2 was determined.The Curie temperature was 165 K,and its significant perpendicular magnetic anisotropy was confirmed.(2)Study on the anomalous Hall Effect of Fe3GeTe2/WTe2 heterostructure.By optimizing the fabrication process of the heterostructure,Fe3GeTe2/WTe2 heterostructure devices were prepared.Through anomalous Hall tests,the low-temperature ferromagnetism of the Fe3GeTe2/WTe2 hetero structure was determined,with a Curie temperature of 150 K and strong perpendicular magnetic anisotropy.In the anomalous Hall test under different bias currents,it was found that the coercive force of the Fe3GeTe2/WTe2 heterostructure decreases with increasing current,and the gradient ?Hc/?JFGT of the coercivity reduction reaches 0.55 kOe MA-1 cm2 at 10 K.According to our analysis,this phenomenon is mainly due to the influence of Joule heat during the test.The excessive Joule heat may be caused by the large contact resistance generated by the structure of the heterojunction device,the low thermal conductivity of the van der Waals heterostructure interface and the large thermal resistance caused by bubbles in the interface.(3)Study on the magnetoresistance effect of Fe3GeTe2/WTe2 heterostructure.It is found that the magnetoresistance curve of Fe3GeTe2/WTe2 heterostructure exhibits anti-symmetric magnetoresistance.By comparing the anomalous Hall curve and magnetoresistance curve of the device,the appearance of antisymmetric magnetoresistance is due to the appearance of magnetic domain walls in magnetic materials.Anomalous Hall resistance antisymmetric inversion results in mixed magnetoresistance antisymmetric phenomena.The anti-symmetric magnetoresistance also disappears with the disappearance of the anomalous Hall resistance.