Interfacial atomic layers for full emergence of interfacial Dzyaloshinskii–Moriya interaction

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.