Electrical Control of 2D Magnetism in Bilayer CrI3

Abstract: The challenge of controlling magnetism using electric fields raises fundamental questions and addresses technological needs such as low-dissipation magnetic memory. The recently reported two-dimensional (2D) magnets provide a new system for studying this problem owing to their unique magnetic properties. For instance, bilayer chromium triiodide (CrI3) behaves as a layered antiferromagnet with a magnetic field-driven metamagnetic transition. Here, we demonstrate electrostatic gate control of magnetism in CrI3 bilayers, probed by magneto-optical Kerr effect (MOKE) microscopy. At fixed magnetic fields near the metamagnetic transition, we realize voltage-controlled switching between antiferromagnetic and ferromagnetic states. At zero magnetic field, we demonstrate a time-reversal pair of layered antiferromagnetic states which exhibit spin-layer locking, leading to a remarkable linear dependence of their MOKE signals on gate voltage with opposite slopes. Our results pave the way for exploring new magnetoelectric phenomena and van der Waals spintronics based on 2D materials.

• The paper demonstrates voltage-controlled switching between AFM and FM states in bilayer CrI3, achieving a ~30% change in the critical magnetic field.
• Advanced magneto-optical Kerr effect microscopy revealed spin-layer locking and linear gate voltage dependence of magnetic signals at zero field.
• The findings offer a promising pathway for energy-efficient spintronic devices and novel magnetoelectric applications in 2D materials.

Electrical Control of 2D Magnetism in Bilayer CrI3: An Analytical Overview

This essay presents an overview of the research paper "Electrical Control of 2D Magnetism in Bilayer CrI3," which explores the intriguing field of electrically tunable magnetism in two-dimensional (2D) materials. The study specifically focuses on bilayer chromium triiodide (CrI3), a layered antiferromagnetic material exhibiting unique magnetoelectric phenomena. The findings have both theoretical implications for understanding 2D magnetism and practical applications in spintronics.

The research demonstrates electrical control over magnetism in CrI3 bilayers, achieved through electrostatic gating and probed using advanced magneto-optical techniques like the magneto-optical Kerr effect (MOKE) microscopy. The bilayer CrI3 system, characterized by a low Néel temperature of ~45 K, serves as a model for studying the transition between antiferromagnetic (AFM) and ferromagnetic (FM) states in response to electrical stimuli.

The paper highlights the realization of voltage-controlled switching between AFM and FM states at fixed magnetic fields near the metamagnetic transition. Interestingly, at zero magnetic field, the researchers have identified time-reversal pairs of layered AFM states exhibiting spin-layer locking, leading to a linear dependence of the MOKE signals on gate voltage. This variation is marked by slopes of opposite signs, which could enable novel magnetoelectric phenomena and advancements in van der Waals spintronics leveraging 2D materials.

Key results include the demonstration that the critical magnetic field for the metamagnetic transition between AFM and FM states can be tuned by approximately 30% through electrostatic gating. The metamagnetic transition exhibits a strong dependence on doping levels, as established by dual-gate structures that enable independent control over carrier concentration and displacement electric field. This suggests that the modulation of orbital occupation and magnetic anisotropy via doping is the primary mechanism driving the gate-tunable magnetic phase transition in bilayer CrI3.

Moreover, the research uncovers electrical control of layered AFM states at zero magnetic field, achieved by preparing the system into distinct time-reversal AFM states (notably labeled as states  and ). This establishes full electrical tunability over the AFM configurations, underscoring the potential for transitioning between spin configurations without an external magnetic field by merely adjusting gate voltages.

The implications of these findings extend to the field of spintronics, where gate-tunable 2D magnetism could underpin architectures for low-energy magnetic memory and logic devices. Further, the understanding of spin-layer locking effects and the tunability of AFM states might stimulate novel applications, including magnetoelectric devices and magneto-optic modulators.

As a forward-looking perspective, this work beckons theoretical investigations into the modulation effects of doping on 2D magnetic materials, underscoring the importance of material engineering at atomic scales to achieve desired electronic and magnetic properties. Additionally, practical device implementations could lead to the exploration of coupling these effects with other 2D materials to develop multifunctional heterostructures tailored for specific technological roles.

In conclusion, the paper sets a foundation for future explorations of electrical control over 2D magnetism, positioning bilayer CrI3 as a promising candidate for spintronic applications demanding high tunability and low power consumption. The study bridges key aspects of fundamental magnetic phenomena and futuristic material applications, contributing significantly to both theoretical understanding and technological advancements.