F-p Hybridization-Induced Ferromagnetism for Ultrathin Two-Dimensional Ferromagnetic Half-Metal (EuN) Monolayer: A First-Principles Study

By performing first-principles calculations, we predicted a kind of novel ultrathin two-dimensional (2D) ferromagnet, single-atomic-layer EuN. EuN monolayer is a ferromagnetic half-metal with a large band gap of 1.69 eV; Eu ions in EuN are in the highest spin state and have large magnetic moments of 6 μB, much larger compared with the non-rare-earth (RE) metal ions. The magneto-crystalline anisotropy energy (MCE) of EuN monolayer is −3.72 meV per Eu ion, which is much higher than that of CrI3 monolayer (0.685 meV per Cr ion); the magnetic dipolar energy (MDE) enhances magnetic anisotropy for EuN monolayer; large magnetic anisotropy energy (MAE) is beneficial to stabilizing the long-range ferromagnetic ordering. More importantly, different from many RE metal monolayers, hybridization between Eu-f and N-p orbitals induces ferromagnetism for EuN monolayer; the Curie temperature of EuN monolayer is above the liquid-nitrogen temperature (100 K). Additionally, the Curie temperature of EuN monolayer increases with increasing biaxial strain due to increased f-p hybridization.