FeSi₂: a two-dimensional ferromagnet containing planar hexacoordinate Fe atoms.

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Planar hypercoordinate atoms represent an unconventional bonding pattern beyond traditional chemistry.
• The concept has been extended from molecular systems to two-dimensional (2D) periodic systems.

Purpose of the Study:

• To predict and characterize a novel stable 2D material with planar hypercoordinate atoms.
• To investigate the stability, electronic, and magnetic properties of the predicted material.
• To explore the feasibility of its synthesis on a semiconductor substrate.

Main Methods:

• First-principles calculations were employed to predict the material's structure and properties.
• Stability was assessed through thermal and kinetic analyses.
• Electronic and magnetic properties were calculated.
• Growth on a silicon (110) substrate was simulated.

Main Results:

• A stable FeSi₂ monolayer with planar hexacoordinate Fe atoms was predicted.
• The monolayer exhibits abundant multicenter bonds, leading to excellent thermal and kinetic stability.
• Anisotropic mechanical properties and room-temperature ferromagnetism (T_C ~360 K) were observed.
• Feasible direct growth on a Si (110) substrate was demonstrated, preserving the monolayer's properties.

Conclusions:

• The FeSi₂ monolayer represents a new class of 2D materials with planar hypercoordinate atoms.
• Its unique properties make it a promising candidate for spintronic devices.
• The compatibility with silicon technology facilitates potential integration into semiconductor devices.