Metal-Free Ferromagnetism in Triangulene Two-Dimensional Frameworks

Area of Science:

• Materials Science
• Organic Chemistry
• Condensed Matter Physics

Background:

• Achieving room-temperature ferromagnetism in purely organic two-dimensional (2D) materials is a significant scientific challenge.
• Existing organic magnets often lack stability or require specific conditions.

Purpose of the Study:

• To introduce a novel mixed-topology strategy for inducing strong ferromagnetic (FM) coupling in metal-free 2D frameworks.
• To design and computationally investigate new organic 2D materials with intrinsic FM order.

Main Methods:

• Covalently connecting non-Kekulé polycyclic aromatic hydrocarbon (PAH) radicals with distinct sublattice topologies.
• Utilizing first-principles calculations to analyze the electronic and magnetic properties of designed 2D frameworks.
• Investigating the role of symmetry breaking (inversion and time-reversal) in achieving FM order.

Main Results:

• Designed 32 novel FM 2D frameworks with spin-1/2 and hybrid spin-1/2-spin-1 honeycomb lattices.
• These organic 2D frameworks exhibit robust ferromagnetism as semiconductors with tunable spin-dependent bandgaps (0.9–3.8 eV).
• Achieved record-high FM couplings (up to 127 meV), spin-splitting energies (>2 eV), and Curie temperatures (>550 K), ensuring stability far beyond room temperature.

Conclusions:

• The mixed-topology strategy effectively induces strong intrinsic FM order in metal-free 2D materials.
• The designed organic 2D frameworks offer a promising platform for flexible magnets with applications in spintronics and quantum technologies.
• Established a design principle for metal-free FM semiconductors based on π-conjugated networks.