Electrical control of antiferromagnetism is highly desirable for realizing low-cost and high-density spintronic devices, yet it remains a major challenge in conventional multiferroics. Here we propose a type-III multiferroics, where antiferromagnetism is driven by ferroelectric polarization, providing a potential route for controlling antiferromagnetism via electric fields. We reveal that the emergence of electric polarization could greatly change the crystal field splitting, which alters spin occupation states and, thus, induces antiparallel aligned atomic magnetic moments. Using first-principles calculations, we predict ferroelectricity-driven antiferromagnetism in a ${\mathrm{NbS}}_2$ bilayer intercalated by Ti atoms [denoted as $\mathrm{Ti}{\left({\mathrm{NbS}}_2\right)}_2]$. In the nonpolar AA stacking configuration, the two spins of $\mathrm{T}{\mathrm{i}}^{2+}$ ions are paired in the lowest singlet $d_{z2}$ orbital owing to the trigonal prismatic crystal field, leading to zero magnetic moment. While in the AB configuration with an out-of-plane polarization of 1.34 $\mu \mathrm{C}/\mathrm{c}{\mathrm{m}}^2$, the two spins are parallel in the triplet ${\mathrm{t}}_{2g}$ levels generated by the octahedral crystal field, giving rise to an atomic magnetic moment of 2 μ${}_B$ per Ti and a stripy-antiferromagnetic ground state. The discovery of antiferromagnetic type-III multiferroics would open an innovative pathway for realizing next-generation spintronic devices.

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• Intercalation
• Magnetoelectric effect
• 2-dimensional systems
• Multiferroics
• First-principles calculations