Tunable Magnetic Response in 2D Materials via Reversible Intercalation of Paramagnetic Ions

The unique properties of 2D materials spur fundamental studies and advanced technologies. As one of the important properties, magnetism is highly desired to be incorporated into various 2D materials for an active magnetic response, yet it remains challenging to develop a generalized and controllable method to magnetize a wide-range of 2D materials reversibly. In this work, a reversible magnetization method is demonstrated for introducing the active magnetic response to various 2D material multilayers, ranging from graphene oxide (GO) to montmorillonite, titanium carbide (MXene), molybdenum disulfide (MoS₂), and metal–organic framework, via the de-/intercalation of holmium ions (Ho³⁺). The magnetic response can be tuned up to eight- to tenfold increases of the magnetic susceptibilities in all 2D materials by simply controlling the soaking time in the Ho ion solution. Moreover, the magnetic response can be quickly reversed by undergoing a rinsing process in dilute acids together with the recovery of intrinsic physicochemical properties of 2D materials. As a result, the improved magnetic response allows manipulation of the magnetized 2D materials, enabling the development of a magnet-assisted transfer process for large-area 2D material films as well as the fabrication of magnetically responsive 2D material actuators.