An Effective Tight-Binding Model with Reduced Lattice Sites from First-Principles for Low-Loss Magnet V(TCNE)₂ and Other Organic Ferrimagnets

Vanadium tetracyanoethylene, V(TCNE)₂, is a room temperature ferrimagnetic semiconductor with a T_c ~ 600 K, known for its very low loss ferromagnetic resonance and efficient spin-wave propagation. [1,2,3] Recent discoveries of VTCNE's permanent porosity and its ability to incorporate dopant molecules have expanded its potential applications in new magnetic devices. [4] In this work, we use DFT code VASP and hybrid functional Heyd-Scuseria-Ernzerhof (HSE06) to explore the various electronic and magnetic properties of both doped and undoped VTCNE, as well as similar materials such as vanadium tetracyanobenzene (VTCNB) and other organic ferrimagnets. [5,6,7,8] A simple effective tight-binding model of VTCNE is constructed, featuring 9 spin up and 3 spin down bands across 3 distinct lattice sites. This allows us to efficiently model the band structure and transport properties, enabling quick and effective calculations of more complex systems (such as doped VTCNE or similar materials) and providing insights beyond the capabilities of DFT alone, particularly for device-level modeling.