Antiferromagnetic Single Chain CrCl₂

Bulk CrCl₂ is a quasi-one dimensional orthorhombic crystal consisting of 1D chains of Cr atoms in an antiferromagnetic (AFM) ground state. Density functional theory calculations show that the exfoliation energy is small, and the phonon spectrum and ab-initio molecular dynamics calculations show that single chains of CrCl₂ are stable. The single chains are planar, they retain the AFM ground state of the bulk, and the magnetic anisotropy results in the spins aligning perpendicular to the plane of the chain. First and second neighbor exchange constants and anisotropy constants for the isolated chain are extracted from total energy calculations. The exchange constants are nearly isotropic, so that an isotropic Heisenberg model with single-ion magnetic anisotropy is used to derive analytical expressions for the magnon spectrum. Since the spectrum is gapped due to the anisotropy, renormalized spin wave theory is used to determine the Néel temperature of the AFM single-chain CrCl₂. The resulting Néel temperature is similar to that of the bulk crystal.