Interfacial phenomena play decisive roles in modern science and technology as the scale of the material shrinks down to a few atomic layers. Such minute nanostructures require a more comprehensive understanding beyond the conventional concepts of interfaces and interfacial phenomena generated at interfaces. From a series of a few-atomic-layer-thick magnetic films, we experimentally demonstrate that, contrary to the common notion, interfacial phenomena require a finite thickness for their full emergence. The layer-thickness dependences reveal that the interfacial Dzyaloshinskii–Moriya interaction (DMI) begins to appear with increasing thickness, and emerges completely at a thickness of 2–3 atomic layers, at which the magnitude is maximized. This result implies that the DMI is suppressed when the “bulk” layer adjacent to the interface is thinner than the threshold thickness. The existence of the threshold thickness indicates the need to refine conventional perspectives on interfacial phenomena, and imposes the lowest structural bound and optimum thickness to maximize interfacial effects for technological applications.

随着材料规模缩小到几个原子层，界面现象在现代科学技术中起着决定性的作用。除了常规的界面概念和在界面处产生的界面现象之外，这种微小的纳米结构还需要更全面的理解。从一系列几个原子层厚的磁性膜中，我们实验证明，与通常的概念相反，界面现象需要有限的厚度才能完全出现。层厚度的依赖关系表明，界面Dzyaloshinskii-Moriya相互作用（DMI）随着厚度的增加而开始出现，并在2-3个原子层的厚度处完全出现，并在此厚度处最大化。该结果表明，当与界面相邻的“体”层比阈值厚度薄时，DMI被抑制。阈值厚度的存在表明需要完善关于界面现象的常规观点，并施加最低的结构界限和最佳厚度以最大化技术应用的界面效果。