Stable ferromagnetism and half-metallicity in two-dimensional polyporphyrin frameworks

Two-dimensional (2D) organic materials with stable electron spin polarization, ferromagnetic ordering and half-metallicity are quite promising for spintronics, due to their long spin coherence length and mechanical flexibility. Here, using porphyrin molecules as building blocks, we propose a novel 2D periodic organic nanomaterial (2D-polyporphyrin) from first-principles calculations. The recent experimental progress on the one-dimensional (1D) Zn-porphyrin arrays hints the plausibility of these 2D polyporphyrin frameworks. We show that electron spin-polarization can be achieved in both metal-free and transition-metal-embedded 2D-polyporphyrins. Cr-polyporphyrin (Cr-PP) in particular has stable ferromagnetic ordering with a Curie temperature (Tc) of about 187 K as indicated by the Monte Carlo simulations based on the 2D Ising model, which is much higher than that reported in the 2D Mn-phthalocyanine framework. The ferromagnetic Cr-PP nanosheet can be tuned to half-metallic by electron doping. The present work opens up an avenue for the development of 2D organic nanostructures with stable ferromagnetism and half-metallicity.