Novel two-dimensional magnets with an in-plane auxetic effect

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Auxetic materials possess a negative Poisson's ratio, expanding when stretched.
• Two-dimensional (2D) materials offer unique electronic and mechanical properties.
• Combining auxeticity with magnetism in 2D materials is underexplored.

Purpose of the Study:

• To investigate auxetic behavior in a new class of 2D magnets.
• To understand the origin of auxeticity in these materials.
• To explore the interplay between auxeticity, magnetism, and strain.

Main Methods:

• Density-functional-theory (DFT) calculations were employed.
• Dynamic stability and mechanical properties were assessed.
• Electronic coupling and magnetic ordering under strain were analyzed.

Main Results:

• Squarely packed transition metal dichlorides (MCl2) exhibit intrinsic in-plane auxeticity.
• Auxetic behavior is attributed to weak bond stiffness from electronic coupling.
• Magnetic ordering in auxetic 2D magnets is robust against strain.

Conclusions:

• The auxetic effect in MCl2 is linked to electronic structure, not just crystal packing.
• Auxeticity enhances the robustness of magnetic ordering by preserving crystal symmetry.
• These auxetic 2D magnets hold potential for novel nanodevice applications.