Multiferroic Properties of Rare-Earth-Doped VOCl2 Monolayers: A First-Principles Study

The structural and electronic properties of the rare-earth-modified VOCl2 monolayer (V1−xXxOCl2, where X = Nd, Sm and Eu) are explored, by using the density functional theory calculations. In particular, the influence of the rare-earth (X) concentration on the physical properties is investigated for x=0.166, 0.083, and 0.062. The lattice parameters for all the optimized structures reveal an increase, while the crystal structure changes from rectangular (with Pmm2 space-group) to oblique for the x=0.166 concentration, preserving the original space-group for the other compositions. The structural analyses also revealed moderate changes in the VO2Cl4 distortions, after the inclusion of the rare-earth elements. On the other hand, the electronic properties have shown that the substitution of V by the Nd, Sm and Eu cations also preserves the semiconductor behavior of the studied system. The obtained results for the density of state reveal a non-zero total magnetization and show that the inclusion of the X cations promotes a transition from the antiferromagnetic to the ferrimagnetic state in the V1−xXxOCl2 compositions. Furthermore, the modern theory of polarization reveals the ferroelectric character for the pure and modified system. These results show that the controlled substitution at the V-site with rare-earth elements simultaneously modifies the structural, electronic, magnetic and multiferroic properties of the VOCl2 system, offering promising potential of the studied system for application in 2D-based materials and electronic devices with enhanced multifunctional properties.