Emerging magnetism in stacked vdW heterostructures between layered antiferromagnets

Van der Waals (vdW) magnet heterostructures have emerged as new platforms to explore exotic magnetic orders and quantum phenomena. We have observed emerging magnetism with perpendicular magnetization in stacked heterostructures between vdW inter-layer antiferromagnets (such as CrI3 or/and CrCl3) that individually no do possess such magnetization. In one of our studies [1], we fabricated twisted double antiferromagnetic bilayer CrI3, and by magneto-optical Kerr effect microscopy demonstrate the coexistence of antiferromagnetic and ferromagnetic orders with nonzero net magnetization, which is the hallmark of moiré magnetism. Such magnetic state exhibits nonmonotonic temperature dependence and extends over a wide range of twist angles with transitions at ~0° and above 20°. We further demonstrate voltage-assisted magnetic switching and the linear magnetoelectric effect. The observed nontrivial magnetic states and unprecedented control by twist angle, temperature and electrical gating are supported by the simulated phase diagram of the moiré magnetism. The results illustrate the rich behaviors of twisted antiferromagnets and the control over them, and add significantly to the emerging study of twisted/Moire magnets exhibiting noncollinear states and novel domain structures. In another study [2], we made heterostructures of layered antiferromagnets, CrI3 and CrCl3, with perpendicular and in-plane magnetic anisotropy, respectively. Using magneto-optical Kerr effect microscopy, we demonstrate out-of-plane magnetic order in the CrCl3 layer proximal to CrI3, with ferromagnetic interfacial coupling between the two. Such an interlayer exchange field leads to higher critical temperature than that of either CrI3 or CrCl3 alone. We further demonstrate significant electric-field control of the coercivity, attributed to the naturally broken structural inversion symmetry of the heterostructure allowing unprecedented direct coupling between electric field and interfacial magnetism. These findings illustrate another new opportunity to explore exotic magnetic phases and engineer spintronic devices in vdW heterostructures.