Electric Field Effect in Multilayer Cr2Ge2Te6: a Ferromagnetic Two-Dimensional Material

Abstract: The emergence of two-dimensional (2D) materials has attracted a great deal of attention due to their fascinating physical properties and potential applications for future nanoelectronic devices. Since the first isolation of graphene, a Dirac material, a large family of new functional 2D materials have been discovered and characterized, including insulating 2D boron nitride, semiconducting 2D transition metal dichalcogenides and black phosphorus, and superconducting 2D bismuth strontium calcium copper oxide, molybdenum disulphide and niobium selenide, etc. Here, we report the identification of ferromagnetic thin flakes of Cr2Ge2Te6 (CGT) with thickness down to a few nanometers, which provides a very important piece to the van der Waals structures consisting of various 2D materials. We further demonstrate the giant modulation of the channel resistance of 2D CGT devices via electric field effect. Our results illustrate the gate voltage tunability of 2D CGT and the potential of CGT, a ferromagnetic 2D material, as a new functional quantum material for applications in future nanoelectronics and spintronics.

Electric Field Effect in Multilayer Cr[_2]Ge[_2]Te[_6]: A Study of a Ferromagnetic Two-Dimensional Material

This paper presents a comprehensive exploration of Cr[_2]Ge[_2]Te[_6] (CGT) as a ferromagnetic two-dimensional (2D) material, focusing on its preparation, characterization, and potential applications in nanoelectronics and spintronics through the electric field effect. The emergence of 2D materials has heralded a new era in material science, particularly following the isolation of graphene. CGT adds to the family of emerging 2D materials by offering room for expansive research and practical applications due to its unique ferromagnetic properties.

Key Findings

• Preparation and Characteristics of Few-layer CGT: The study successfully synthesized high-quality CGT single crystals and prepared 2D CGT flakes with thicknesses down to a few nanometers. These efforts achieved via mechanical exfoliation were critical to examining the electrical and magnetic properties of thin film CGT. Notably, the authors report a Curie temperature of approximately 61 K for single-crystal CGT.

• Electric Field Modulation: The work demonstrates significant modulation of channel resistance in CGT devices as influenced by gate voltage, showcasing the material’s potential for electric field control. This effect was particularly notable in thinner flakes, which exhibited substantial changes in resistance, signifying their susceptibility to electronic state modifications through Fermi level adjustment. The study observed a heightened gating effect leading to pronounced changes, from semiconducting to a more conductive state, under external electric fields.

• Magnetic Properties: Utilizing magneto-optic Kerr effect (MOKE) measurements, the authors confirmed the ferromagnetic nature of CGT flakes, noting that even thin layers retained a Curie temperature analogous to that of the bulk material. The study also utilized the anomalous Hall effect to investigate the magnetic characteristics of CGT, revealing ferromagnetic properties under gate-tuned conditions.

Implications and Future Prospects

The implications of this research are significant in advancing the understanding and utility of 2D magnetic materials. The capability to modulate electronic properties using an electric field augments CGT's appeal for integration into spintronic devices, offering new pathways to manipulate spin currents. Practically, the incorporation of CGT into van der Waals heterostructures can foster the development of novel electronic and spintronic components.

This study suggests the potential of CGT in exploring quantum phenomena such as the quantum anomalous Hall effect when combined with Dirac materials like graphene. Furthermore, the electric field control of magnetism hints at future applications in low-power memory devices, known as magnetoresistive devices. The opportunity to tune the ferromagnetic properties, such as Curie temperature and magnetic anisotropy, remains a fertile area for theoretical and experimental investigation, particularly with approaches that could enhance the isolation quality of CGT, such as encapsulation strategies.

In conclusion, this research adds a crucial dimension to the study of 2D materials, highlighting the versatility and promising future of CGT in nanotechnology. Enhanced sensitivity measurements and protection against oxidation may further unlock its potential for various functional applications in future electronic and spintronic devices. The research opens avenues for further exploration into 2D magnetic materials' capabilities, propelling advancements in quantum computing and energy-efficient electronics.