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

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Chemistry

Background:

• Two-dimensional (2D) magnetic materials offer advantages over diluted magnetic semiconductors for spintronics.
• Intrinsic ferromagnetism in 2D materials is crucial for controllable spintronic devices.
• The novel 2D Janus-CrGeS₂ monolayer presents unique structural, electronic, and magnetic properties.

Purpose of the Study:

• To investigate the structural, electronic, and magnetic properties of the 2D Janus-CrGeS₂ monolayer.
• To assess the stability and potential applications of this novel 2D magnetic material.
• To explore the origin of ferromagnetism and its characteristics in CrGeS₂.

Main Methods:

• First-principles calculations using density-functional theory (DFT) with VASP code.
• Employing PAW pseudopotentials, GGA-PBE, and DFT+U for exchange-correlation and Cr 3d interactions.
• Utilizing HSE06 for electronic properties and Phonopy code for phonon calculations; ab initio molecular dynamics for thermal stability.

Main Results:

• The Janus-CrGeS₂ monolayer is dynamically, structurally, mechanically, and thermally stable.
• Electronic structure calculations reveal low bandgaps (0.01-0.054 eV) with GGA-PBE/HSE06, increasing to 0.23 eV (indirect) with Hubbard correction.
• A ferromagnetic ground state with a net magnetic moment of 8.6 μB was observed, originating from sp-d exchange coupling near the Fermi level.
• The material exhibits a half-metallic character and a high Curie temperature of 1245 K.

Conclusions:

• The 2D Janus-CrGeS₂ monolayer is a stable intrinsic ferromagnetic material with potential for spintronics.
• Its half-metallic nature and high Curie temperature make it suitable for high-temperature magnetic applications.
• The study provides insights into the electronic structure and magnetic properties governed by crystal field theory and exchange coupling.