Electrically tunable moir\'e magnetism in twisted double bilayer antiferromagnets

The introduction of moir\'e superlattices to electronic materials can dramatically alter electronic properties, promising emergent correlated and topological phenomena. Its first demonstration in van der Waals magnets exhibited noncollinear states and domain structures with, however, limited manipulation. Here, 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 moir\'e magnetism. Such magnetic state exhibits nonmonotonic temperature dependence and extends over a wide range of twist angles with transitions at ~0{\deg} and above 20{\deg}. 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 method are supported by the simulated phase diagram of the moir\'e magnetism. Our results illustrate the rich behaviors of twisted antiferromagnets and the control over them.