First-principles study on the structural, electronic, and magnetic properties of two-dimensional Janus CrGeS₂

Two-dimensional (2D) magnetic materials presenting intrinsic ferromagnetism are well considered giving controllable limitations of standard diluted magnetic semiconductors for use in spintronics devices. Novel 2D Janus-CrGeS₂ monolayer was made on the findings of structural, electronic and magnetic properties. The material is known to be dynamically, structurally, mechanically and thermally stable. The electronic structure formations point that CrGeS₂ exhibits direct but low bandgaps of 0.01 eV and 0.054 eV as per directions of GGA-PBE and HSE06 that is increased to 0.23 eV with indirect bandgap in the existence of Hubbard modification. The findings reported that the material specifies a ferromagnetic ground state with an outstanding net magnetic moment of 8.6 μB. The ferromagnetism originates from the sp-d exchange coupling close to the Fermi level. The crystal field theory reveals that the trigonal non-planar management of sulfur ligands across Cr³⁺ results in a particular d orbital splitting. The material shows the small bandgap half-metallic character. The material displays the largest Curie temperature of 1245 K indicating the stronger ferromagnetism giving its potential for high-temperature magnetic applications.

First-principles calculations were performed using density-functional theory (DFT) as implemented in VASP code. PAW pseudopotentials, the GGA-PBE, functional, and Hubbard correction (DFT + U) were employed to account for exchange-correlation and strong Cr 3d interactions. We also performed electronic properties using the HSE06 functional. Spin-polarized calculations were performed for para-, ferro-, and antiferromagnetic states. Phonon calculations were assessed by Phonopy code, while thermal stability was explored via ab initio molecular dynamics in the canonical (NVT) ensemble using the Nose-Hoover thermostat.