Theoretical study of the stability and magnetic anisotropy of CrX 3 (X = Cl, Br, I) nanotubes

Abstract Inorganic nanotubes (NTs) derived from two-dimensional materials, especially CrI 3 NTs, exhibit promising application in the fields of spintronics and optical nanodevices due to their unique magnetic and optical properties. Here, the correlation between curvature and formation energy is systematically investigated for CrI 3 NTs with different chiral indices. Further study on the interaction between CrI 3 NTs and the nested carbon NTs (CNTs) reveals that CNT encapsulation can significantly improve the structural stability of CrI 3 NTs. The CrX 3 (X = Cl, Br, I) monolayer structure exhibits axial magnetic anisotropy energy (MAE), with its lowest free energy distributed along the z -axis. In contrast, CrI 3 NTs with a tube radius ranging from 5 Å to 28 Å show in-plane magnetic anisotropy, where the lowest free energy exists in the xy -plane, and the absolute value of the MAE increases as the curvature increases. When the curvature is greater than 0.11, the absolute value of MAE is higher than that of the plane. With further exploration of CrCl 3 NTs and CrBr 3 NTs, it is found that the MAE of NTs with a tube radius within 28 Å also increases with the increase of compressive strain. Through the analysis of symmetry and orbital contribution of MAE, the physical mechanism behind the differences in magnetic anisotropy is clarified.