Electric-field control of magnetism in few-layered van der Waals magnet (1802.06255v1)

Abstract: Manipulating quantum state via electrostatic gating has been intriguing for many model systems in nanoelectronics. When it comes to the question of controlling the electron spins, more specifically, the magnetism of a system, tuning with electric field has been proven to be elusive. Recently, magnetic layered semiconductors have attracted much attention due to their emerging new physical phenomena. However, challenges still remain in the demonstration of a gate controllable magnetism based on them. Here, we show that, via ionic gating, strong field effect can be observed in few-layered semiconducting Cr${2}$Ge${2}$Te$_{6}$ devices. At different gate doping, micro-area Kerr measurements in the studied devices demonstrate tunable magnetization loops below the Curie temperature, which is tentatively attributed to the moment re-balance in the spin-polarized band structure. Our findings of electric-field controlled magnetism in van der Waals magnets pave the way for potential applications in new generation magnetic memory storage, sensors, and spintronics.

• The paper demonstrates that electric fields can effectively modulate magnetism in few-layered Cr2Ge2Te6 below its Curie temperature using distinct gating methods.
• The study employs micro-area Kerr measurements and DFT simulations, revealing a two-fold reduction in saturation fields with ionic gating.
• The findings indicate promising spintronic applications by enabling precise magnetic state tuning for low-power magnetic memory devices.

Electric-Field Control of Magnetism in Few-Layered Van der Waals Magnet

The research paper presents an investigation into the electric-field control of magnetism in few-layered van der Waals (vdW) magnetic semiconductors, specifically focusing on few-layered Cr$_{2}$Ge$_{2}$Te$_{6}$ (CGT) devices. These novel layered magnetic compounds, which operate within the Curie temperature, have demonstrated significant potential for exploiting new physical phenomena related to spintronics and next-generation magnetic memory applications. The authors employ both solid-state and ionic gating mechanisms to manage the magnetization properties of CGT, noting distinguishable effects between the two approaches when controlling spin interactions via electric fields.

Key Findings and Results

1. Layered Magnetism and Electric Gating: The paper delineates the potential of electrically controlling magnetization in few-layered vdW semiconductors, a property that remains critical for advancements in spintronic applications. The paper identifies that Cr$_{2}$Ge$_{2}$Te$_{6}$ devices can maintain conductivity and gate tunability below their ferromagnetic Curie temperature.
2. Kerr Measurements: Utilizing micro-area Kerr measurements, it was observed that tunable magnetization loops were effectuated below the Curie temperature for ionic liquid gated devices. The researchers demonstrate that ionic gating, as opposed to solid-state gating, can induce significant shifts in magnetic properties, evidenced by changes in magnetization loops, and a pronounced variation in saturation fields ($H_s$) under different gate voltages.
3. Theoretical Modeling: Complementary density functional theory (DFT) simulations provide insights into the spin-polarized band structure of CGT. The theoretical results support the experimental findings whereby increased hole doping results in decreased net magnetic moments and saturation magnetization, consistent with the observed tuning of magnetism through gating.
4. Saturation Field Modifications: The empirical observation that saturation fields can be modulated by ionic gating indicates the potential for precise control over magnetic states in layered materials. The results suggest a two-fold reduction in saturation field with increasing gate-induced carrier density, a feature that aligns well with computational predictions.

Implications and Future Directions

The ability to control magnetism in vdW semiconductors through electric fields heralds significant implications for spintronic technologies, potentially enhancing the performance of magnetoresistive devices and enabling the realization of low-power magnetic transistors. This form of control points to possibilities for new device architectures in non-volatile memory storage where magnetic states can be finely tuned via electrostatic doping.

The research opens avenues for further exploration into other vdW materials, expanding upon the diversity of extrinsically tunable magnetic properties while also refining ionic gating techniques to optimize the electric field effects in 2D materials. Future advancements could look into heterostructure designs combining different layered compounds, leveraging synergistic effects between varied material properties to yield advanced functional devices. Additionally, long-term stability and scalability assessments will be crucial for practical applications.

In conclusion, this paper demonstrates a compelling method for the electric control of magnetism in few-layered vdW magnets, marking a notable step towards integrating these materials into current and forthcoming technological paradigms in the spintronic sector.