Electron doping in non-magnetic YH3 leads to room temperature ferromagnetism and a flat band: insights from density functional theory

Abstract

Herein, we investigated the origin of induced room temperature d⁰ ferromagnetism in YH₃ doped with B (2μ_B per defect magnetic moment) using density functional theory (DFT) simulations. The prediction of d⁰ ferromagnetism in non-magnetic YH₃ using the generalized gradient approximation functional was further confirmed using the hybrid HSE06 functional. Interestingly, B doping in the system led to the appearance of a flat band, which may be due to electron doping in the system. The presence of a flat band at the Fermi level may lead to stable ferromagnetism in the system. We found that YH₃ attained 2.0μ_B magnetic moment per defect using a single B atom with an impurity concentration of 1.04 at%. The partial density of states along with the spin-density plot implied that the induced magnetic moment was the result of the interaction between the localized 2p and 4d orbitals of the impurity B and host Y atoms, respectively, within the doped system, satisfying the Stoner criteria for induced ferromagnetism. Ferromagnetism in the system at room temperature was estimated by calculating the Curie temperature, which was around T_c = 510 K, using the mean field approximation. The thermodynamic and dynamic stabilities of the system at 25 GPa were confirmed using ab initio MD simulation and phonon dispersion, respectively. All these results indicate the experimental feasibility of the system as a spintronic device, and we propose that electron doping may be a possible route for designing materials with interesting properties.