Twist engineering—the alignment of two-dimensional (2D) crystalline layers with a specific orientation—has led to tremendous success in controlling the charge degree of freedom, particularly in producing correlated and topological electronic phases in moiré crystals^1,2. However, although pioneering theoretical efforts have predicted that non-trivial magnetism^3,4,5 and magnons^6,7 can be made by twisting 2D magnets, the experimental realization of engineering the spin degree of freedom by twisting remains elusive. Here we fabricate twisted double bilayers of a 2D magnet, namely, chromium triiodide (CrI₃), and demonstrate the successful twist engineering of 2D magnetism in them. We identify signatures of a new magnetic ground state that is distinct from those in natural two-layer (2L) and four-layer (4L) CrI₃. We show that for a very small twist angle, this emergent magnetism can be well approximated by a weighted linear superposition of those of 2L and 4L CrI₃, whereas for a large twist angle, it mostly resembles that of isolated 2L CrI₃. However, at an intermediate twist angle, there is a finite net magnetization that cannot be simply inferred from any homogeneous stacking configuration, but emerges because spin frustrations are introduced by competition between ferromagnetic and antiferromagnetic exchange coupling within individual moiré supercells.

扭曲工程——二维 (2D) 晶体层与特定方向的排列——在控制电荷自由度方面取得了巨大成功，特别是在莫尔晶体^1,2中产生相关和拓扑电子相方面。然而，尽管开创性的理论努力已经预测非平凡的磁性^3,4,5和磁振子^6,7可以通过扭转 2D 磁体来制造，但通过扭转来设计自旋自由度的实验实现仍然难以捉摸。在这里，我们制造了二维磁体的扭曲双层双层，即三碘化铬（CrI ₃)，并在其中展示了二维磁性的成功扭曲工程。我们确定了一种新的磁性基态的特征，该特征不同于天然两层 (2L) 和四层 (4L) CrI ₃中的特征。我们表明，对于非常小的扭转角，这种出射磁性可以很好地通过 2L 和 4L CrI ₃的加权线性叠加来近似，而对于大的扭转角，它主要类似于孤立的 2L CrI ₃。然而，在中间扭转角处，存在一个有限的净磁化强度，这不能简单地从任何均匀的堆叠配置中推断出来，而是由于单个莫尔超晶胞内的铁磁和反铁磁交换耦合之间的竞争引入了自旋挫折而出现。