Signatures of magnetic ordering in a multiferroic 2D material from electron tunnelling

In van der Waals magnets such as CrI₃, reducing thickness reshapes spin order and crystal symmetries, illuminating structure–magnetism correlations in the 2D limit [1,2]. Within this framework, intrinsically multiferroic 2D materials add a further lever to couple lattice, charge and spin. Salient examples include CuCrP₂S₆ with room-temperature out-of-plane ferroelectricity down to a few layers and magnetic order at low temperatures [3,4] or helimagnetic NiI₂, recently shown to host strong chiral magnetoelectric effects in the ultrathin limit [5]. Building on these ingredients we target intrinsic platforms where magnetism, stacking and electrostatics can be co-tuned to manipulate coupled ferroic phases.

Vertical tunnelling architectures with multiferroic 2D layers as the tunnel barrier allow phase tracking through spin-filtering and large tunnelling magnetoresistance [2], which provide sensitive readouts of magnetic reorientation and symmetry breaking across phase boundaries [3,7]. Here, we explore the magnetoresistance of such devices as a function of layer number, temperature and magnetic field. These measurements delineate critical temperatures and their thickness dependence, revealing signatures of magnetic reorientation at the 2D limit.

[1] Sivadas N. et al. Nano Lett. 18, 7658–7664 (2018)

[2] Song, T. et al. Science 360, 1214–1218 (2018)

[3] Io, W. F. et al. . Nat. Commun. 14, 7304 (2023)

[4] Wang, X. et al. Nat. Commun. 14, 840 (2023)

[5] Gao, F. Y. et al. Nature 632, 273–279 (2024)