Coexistence of ferroelectricity and antiferroelectricity in 2D van der Waals multiferroic

Abstract Multiferroic materials with a coexistence of ferroelectric and magnetic order have been intensively pursued to achieve the mutual control of electric and magnetic properties toward energy-efficient memory and logic devices. The breakthrough progress of 2D van der Waals magnet and ferroelectric encourages the exploration of low dimensional multiferroics, which holds the promise to understand inscrutable magnetoelectric coupling and invent advanced spintronic devices. However, confirming ferroelectricity with optical techniques is challenging on 2D materials, particularly in conjunction with antiferromagnetic orders in a single-layer multiferroic. The prerequisite of ferroelectric is the electrically switchable spontaneous electric polarizations, which must be proven through reliable and direct electrical measurements. Here we report the discovery of 2D vdW multiferroic with out-of-plane ferroelectric polarization in trilayer NiI2 device, as revealed by scanning reflective magnetic circular dichroism microscopy and ferroelectric hysteresis loop. The evolutions of between ferroelectric and antiferroelectric phase have been unambiguously observed. Moreover, the magnetoelectric interaction is directly probed by external electromagnetic field control of the multiferroic domains switching. This work opens up opportunities for exploring new multiferroic orders and multiferroic physics at the limit of single or few atomic layers, and for creating advanced magnetoelectronic devices.