Structural and Physical properties of 2-dimensional Fe₃GeTe₂

Two-dimensional (2D) magnetic materials have received a considerable attention recently because they offer scientific and technological advancements due to low-dimensional quantization of electronic states. One of the most studied such systems is Fe₃GeTe₂. It crystalizes in a hexagonal structure and is an itinerant ferromagnetic system with a Curie temperature of 220 K of the bulk form and a strong magnetic anisotropy. In this study, the Fe₃GeTe₂ samples were synthesized using a chemical vapor transport method and characterized using TEM, EDAX, and Raman spectroscopy. To tune the electronic properties of 2D materials, strain engineering has been demonstrated as a powerful technique. Here, monolayers or few layers of Fe₃GeTe₂ were transferred on to polyethylene terephthalate (PET) and bent inward (compressive) or outward (tensile) to apply strain. In-situ Raman spectroscopy was utilized to study the effect of both compressive and tensile strain on the vibrational modes of the material. Since the magnetic domains of the magnetic materials are affected by the crystal orientation, polarized Raman spectroscopy was used to study the material. Magnetic phase transition (para to ferro) was explored using Electron paramagnetic Resonance Spectroscopy (EPR). Temperature and magnetic field dependent 4-probe resistance, R(T,B) and thermopower, S(T,B) were measured in the temperature range of 40-300 K and magnetic field -1 to +1 T. R(T) showed a decrease of resistance with decreasing temperature confirming its metallic behavior, while S(T) showed a change of thermopower from its negative value at higher temperatures to a positive value below 180 K. The results of S(B), R(B) and magnetic field dependent Hall Voltage will also be presented.