4f -block elemental-atom-embedded gh−C3N4 monolayers: Large magnetic moment, high-temperature ferromagnetism, and huge magnetic anisotropy energy

Abstract

Two-dimensional (2D) magnetic materials with strong magnetism, long magnetic relaxation times, high temperature ferromagnetism, and large magnetic anisotropy energy (MAE) are promising for applications of nanoscale spintronic devices. Using the spin-orbital coupling density functional theory (DFT) calculations, we investigate the structural stability, electronic structures, and magnetic properties of graphenelike carbon-nitride ($\mathrm{gh}\text{\ensuremath{-}}{\mathrm{C}}_{3}{\mathrm{N}}_{4}$) sheets with the adsorption of whole series of $4f$-block elemental (lanthanide; Ln) atoms. Our results demonstrate that Ln atoms can be stably embedded into/above the center of the cavity of $\mathrm{gh}\text{\ensuremath{-}}{\mathrm{C}}_{3}{\mathrm{N}}_{4}$ monolayer and significantly affect the electronic and magnetic properties. Upon single Ln atom adsorption, all Ln@$\mathrm{gh}\text{\ensuremath{-}}{\mathrm{C}}_{3}{\mathrm{N}}_{4}$ systems show metal character, large spin and orbital magnetic moments, and most of them favor the long-range ferromagnetic ordering. Interestingly, Pr, Nd, Ho adsorbates would possess total magnetic moments of 1.09, 1.47, 6.13 ${\ensuremath{\mu}}_{B}$, high Curie temperatures (${T}_{c}$) of 593, 699, 700 K, large MAEs of 4.89, $\ensuremath{-}17.88$, 21.31 meV/Ln atom, respectively. Based on the electronic structure analyses, we propose that the $4f$ electron hopping between the occupied and unoccupied states around the Fermi level contributes to the large MAE, significant intratomic Ln-$sd$ orbital hybridization with N-$2p$ orbital hybridization gives rise to structural stability, and the coexistence of superexchange and RKKY interactions determines the long-term ferromagnetic coupling between Ln atoms. The present study demonstrates that Ln@$\mathrm{gh}\text{\ensuremath{-}}{\mathrm{C}}_{3}{\mathrm{N}}_{4}$ sheets have significant promise for applications in spintronics such as high density memory devices or for magnetic random access memory.