Topochemical Vertical Growth of 2D Eu2SO2 Single Crystals for Axial-Dependent Magnetoresistance

Two-dimensional (2D) rare-earth (RE) materials have garnered significant attention due to their unique magnetic properties. Vertically grown 2D materials exhibit significant properties such as high-quality crystals and facile integration. However, due to strong interfacial coupling between materials and the substrate and high nucleation barriers, achieving controlled vertical growth of 2D RE materials remains a challenge. Here, an innovative topochemical transformation strategy is employed to synthesize high-quality vertically grown Eu 2 SO 2 single crystals. The ideal structural framework was provided by the vertical growth of Eu 2 O 3 on the c -sapphire substrate for the subsequent synthesis of a Eu 2 SO 2 single-crystal, effectively mitigating the effects imposed by the sapphire substrate steps and enabling polymer-free transfer. The obtained single-crystal Eu 2 SO 2 exhibits a small rocking curve (FWHM = 0.15°) and an ultralow roughness ( R a = 0.17 nm). Notably, the fabricated Eu 2 SO 2 -based devices exhibit an axial-dependent response, demonstrating a substantial in-plane isotropic magnetoresistance (MR > 50%) and a significant out-of-plane anisotropic magnetoresistance (AMR) ratio of 13.5% accompanied by a large coercivity (1.36 kOe). This work provides a universal approach for preparing vertically grown high-quality 2D RE materials and lays a solid foundation for research into their quantum magnetic properties.