Magnetic ground state of CrOCl: A first-principles study

By first-principles calculations, this paper reveals that the antiferromagnetic (AFM) ground state of CrOCl with an orthorhombic structure observed in experiment is mainly due to the competition between the neighboring magnetic exchange interactions (${J}_{i}$'s). The AFM ground state requires that the first and second nearest neighbors (${J}_{1}$ and ${J}_{2}$) are AFM couplings with comparable magnitudes, and that the seventh nearest neighbor $({J}_{7})$ has a certain size of AFM coupling. By using Liechtenstein's density functional theory $(\mathrm{DFT}+U)$ method and appropriately adjusting the on-site exchange $(\mathcal{J})$ parameter, the ${J}_{i}$'s can satisfy these conditions and lead to the experimentally observed AFM ground state (AFM-Exp). The $\mathcal{J}$ parameter changes the energy levels of the Cr-$3d$ orbitals and consequently the energy differences between the orbitals, which in turn impacts the sign and magnitude of ${J}_{i}$'s. By decomposing the ${J}_{i}$'s into orbital contributions, it is shown that introducing the $\mathcal{J}$ parameter significantly reduces the ferromagnetic parts of ${J}_{1}$ and ${J}_{2}$ and converts them to AFM coupling, which leads to the AFM-Exp ground state.