Theoretical Prediction of a Stable 2D Crystal of Vanadium Porphyrin: A Half-Metallic Ferromagnet

We predict a 2D ferromagnetic half-metal based on vanadium porphyrin (V–PP) using first-principles density functional theoretical analysis. We establish the dynamical stability of its planar structure and magnetic ground state through determination of energetics and phonon dispersion. We find that the exchange interaction between spins of nearest neighbor V atoms is mediated by delocalized states of porphyrin and determine its strength from the relative energies of states with ferromagnetic and antiferromagnetic ordering. Using it in an Ising model, our estimate of its Curie temperature (Tc) is 197 K, which is higher than that of 2D manganese phthalocyanine (Mn–Pc) and 2D Cr–PP. With estimated work function of 4.9 eV, moderate in-plane stiffness, and a branch of very low energy flexural modes evident in its phonon dispersion, we find that 2D V–PP is quite suitable for use in flexible spintronic devices.