[Paper Review] Magnetoelectric torque in polar magnetic bilayers

Zhong Shen, Jun Chen+2 more|arXiv (Cornell University)|Jan 13, 2026

Multiferroics and related materials0 citations

TL;DR

The paper introduces magnetoelectric torque (MET) to switch magnetization in polar van der Waals bilayers via pure electric field, independent of spin-orbit coupling, enabling ultrafast picosecond switching with low energy consumption.

ABSTRACT

Energy-efficient fast switching of spin orientations or textures is a core issue of spintronics, which is highly demanded but remains challenging. Different from the mainstream routes based on spin-transfer torque or spin-orbit torque, here we propose another mechanism coined as magnetoelectric torque to switch the magnetization in polar magnetic bilayers via pure electric field. In some magnetic van der Waals bilayers, when the electrostatic energy of polarization can compensate the interlayer magnetic coupling, a magnetoelectric torque is generated to fastly flip spins within a few picoseconds, which is demonstrated by combining the first-principles calculations, analytic model, as well as atomistic simulations. Such a magnetoelectric torque doesn't rely on the spin-orbit coupling and is generally active in polar magnetic homostructures and heterostructures. Our work provides an alternative route to switch magnetization in nanoscale, which may benefit the energy-saving and fast-response spintronic devices.

Motivation & Objective

• Motivate energy-efficient, fast switching of spin orientations without current-induced Joule heating.
• Propose and quantify a pure-electric-field mechanism (MET) in polar magnetic bilayers.
• Establish the dependence of magnetization switching on polarization, interlayer coupling, and electric field.
• Validate MET using first-principles calculations, analytic models, and atomistic spin dynamics simulations.

Proposed method

• Define a spin model Hamiltonian including intralayer and interlayer exchanges, Dzyaloshinskii–Moriya interaction, single-ion anisotropy, and the E·P term coupled to polarization.
• Compute the polarization P_z as a function of interlayer spin angle via DFT, fit to P_z = P_0 − λ(S_A·S_B) = P_0 − λ cosφ.
• Derive the electric-field dependent interlayer energy ε and identify the critical field Ec = 3J_z/λ, with tuning via strain to reduce Ec (e.g., 3.75% strain).
• Perform atomistic Landau-Lifshitz-Gilbert (LLG) simulations to study dynamic switching under E_z, and corroborate with analytic expressions for MET torque T_A ∝ α(3J_z − Eλ) sinφ.
• Show that MET operates maximally near φ ≈ 90° and yields picosecond switching times with THz-like dynamics.

Experimental results

Research questions

• RQ1 Can a pure electric field switch magnetization in polar van der Waals bilayers without relying on spin-orbit coupling?
• RQ2 How does interlayer polarization and exchange coupling balance determine the MET-driven FM↔AFM switching threshold and dynamics?
• RQ3 What are the realistic switching times and energy dissipation for MET in CrISe bilayers under feasible strains and fields?
• RQ4 Is MET robust across easy-plane and easy-axis magnetic configurations in polar vdW bilayers?

Key findings

• MET enables magnetization switching in CrISe bilayer within ~8 ps under E = ±0.2 V/Å.
• P_z depends linearly on the spin alignment with P_z = P_0 − λ cosφ and shows SOC independence.
• Electric-field energy difference Δε_E = E_z ΔP_z can compensate interlayer magnetic coupling, enabling FM↔AFM switching when Eλ > 3J_z.
• Analytic and atomistic results show MET torque T_A ∝ α(3J_z − Eλ) sinφ with maxima at φ ≈ 90°, producing fast switching.
• The switching time τ scales as τ = π α μ_s / [γ(Eλ − 3J_z)], indicating THz-range dynamics and robustness for reasonable α ( Gilbert damping ).
• Energy consumption per switching is estimated to be ∼2×10^−20 J/(100 nm^2), an order of magnitude lower than STT/SOT designs.