Unconventional ferrimagnetism and enhanced magnetic ordering temperature in monolayer CrCl3 by introducing O impurities and Cl vacancies

Abstract Among chromium trihalides, a specific group of layered van der Waals magnetic materials, chromium trichloride (CrCl 3 ) is the only system relatively stable under ambient conditions. This is also observed in reduced dimensionality where the emergence of extrinsic long-range ordered oxidized and Cl-vacancy-defective CrCl 3 phases is experimentally reported. In this work, the magnetic properties of such extrinsic two-dimensional (2D) systems are studied using density functional theory (DFT) calculations, including the electron-electron (U) repulsion interactions, and Monte Carlo (MC) simulations. Once the Cl vacancies are introduced, the results indicate that the monolayer CrCl 3 has a magnetic moment that is enhanced linearly (up to 3.14 μ B /Cr) in the (1-10 %) vacancy concentration range. This determines a strengthening of the ferromagnetic state and a two-fold increase of the Curie temperature (up to 146 K) as valuated from MC simulations. More interestingly, once oxygen extrinsic impurities are considered, the monolayer CrCl 3 structure is hybridized forming a stable ordered phase (O-CrCl 3 ) with oxygen atoms allocated on the Cr atomic layer in the center of the honeycomb ring formed by Cr atoms. The magnetic moments of the O-CrCl 3 system are localized on both Cr and O atoms, with oxygen which is antiferromagnetically coupled with chromium, resulting in a 2D ferrimagnetic hexagonal lattice system with an average magnetic moment of 2.14 μ B /Cr and a high magnetic ordering temperature (110 K) predicted with DFT in the mean field approach.