An international team, including researchers from CNR-SPIN, Seoul National University, The University of Hong Kong, University of L’Aquila, Southeast University studied the magneto-optical properties of multiferroic heterostructure. As reported in ACS Applied Materials & Interfaces (ACS Appl. Mater. Interfaces 2023, 15, 18, 22282-22290; https://doi.org/10.1021/acsami.3c02680), have shown an unusual magneto-optical Kerr effect (a phenomenon where the reflected light shows a polarization change upon reflection from a structure) in a antiferromagnetic and polar heterostructure, namely CrI3/In2Se3/CrI3.
The polarity of the In2Se3 ferroelectric layer and the anti-ferromagnetism of CrI3 layers remove both the mirror and time-reversal symmetry respectively activating the magneto-optical Kerr effect, even if the system shows no net ferromagnetic polarization. Remarkably, the Kerr angle can be reversed either by reversing the electric polarization or by reversing the spin-magnetization in both layers, keeping the polar state of the In2Se3 layer, i.e., following the “perimeter” of the four-state square in the Figure. Therefore, the 2D heterostructure can be exploited as a fundamental memory building block, where information is encoded by either the two ferroelectric or the two time-reversed antiferromagnetic states, and the read-out can be optically performed by exploiting the magneto-optical Kerr effect. The proposed 2D structure, combining ferroelectricity and anti-ferromagnetism, suggests a novel route toward developing high-performing information storage technology.
Schematic diagram of switching behavior of Kerr angle in the CrI3/In2Se3/CrI3 heterostructure, where the blue and green arrows indicate the magnetization direction of CrI3 monolayer and the polarization direction of In2Se3 monolayer respectively, and the blue/orange/grey double-sided arrow depicts the time-reversal/spatial-inversion/time-spatial-inversion symmetry.
