Magnetism Control Of Two-dimensional Fe₃GeTe₂

Iron germanium tellurium(Fe₃GeTe₂)is a new type of layered magnetic metallic material,which has excellent magnetic properties such as large coercive field,high remanence ratio,and high Curie temperature close to room temperature.Therefore,two-dimensional Fe₃GeTe₂has great potential in the development of high-density and low-power spintronic device applications.In recent years,experimental studies have found that the magnetic properties of Fe₃GeTe₂ have a significant dimensionality effect.When the thickness of Fe₃GeTe₂ is reduced to a single layer,the Curie temperature is only 130 K,which limits the development of its practical spintronics applications.So how to increase the magnetic transition temperature of two-dimensional Fe₃GeTe₂ has become one of the important research directions.Interface engineering provides a new degree of freedom for the magnetic control of two-dimensional materials.In spintronics applications,metal/ferromagnetic metal interface plays an important role in improving device performance.Therefore,this paper proposes an effective method for magnetic control of two-dimensional Fe₃GeTe₂by metal interface engineering.The magnetic control of two-dimensional Fe₃GeTe₂ was discussed through reflection magnetic circular dichroism experiments and first-principles calculations.The author analyzed the influence of the metal substrate interface on the two-dimensional Fe₃GeTe₂ferromagnetism,especially the Curie temperature.The experimental results showed that the substrate has a significant modulation effect on the ferromagnetic transition temperature.Fe₃GeTe₂ flakes of different thicknesses were prepared on three substrates of Al,Au and Si O₂by mechanical exfoliation.The reflection magnetic circular dichroism experiments showed a dimensionality effect in Fe₃GeTe₂.The Curie temperature decreased sharply with the thickness,and the saturation magnetization also decreased.Fe₃GeTe₂ with the same thickness exhibited different critical behaviors on different substrates.Compared with the commonly used Si O₂substrate,the Au substrate caused the Curie temperature to increase,while the Al substrate caused the Curie temperature to decrease significantly.The author explained this phenomenon qualitatively through first-principles calculations.Fe₃GeTe₂-metal heterojunction calculations found that the interface coupling caused the average magnetic moment on Fe atoms to decrease by 0.430?_B(Al)and 0.124?_B(Au),respectively.The interface charge transfer played a leading role.From the mean-field approximation theory,the Curie temperatures of bilayer Fe₃GeTe₂-metal heterojunction were found to be 9.27 K(Al)and 32.98 K(Au),respectively.The theoretical calculations confirmed the modulation effect of the substrate on the Curie temperature of two-dimensional Fe₃GeTe₂.Based on the study of the interface coupling of the substrate,the author realized the control of the ferromagnetic transition temperature in two-dimensional Fe₃GeTe₂.This work provides a simple method for permanently adjusting the magnetic properties of two-dimensional materials without external field,and proposes a reliable theoretical model to explain the two-dimensional Fe₃GeTe₂ magnetic behavior changes induced by interface coupling.It has laid a foundation for the application of new two-dimensional spintronic devices.