Electron doping induced stable ferromagnetism in two-dimensional GdI_3 monolayer

As a two-dimensional material with a hollow hexatomic ring structure, N\'eel-type anti-ferromagnetic (AFM) GdI3 can be used as a theoretical model to study the effect of electron doping. Based on first-principles calculations, we find that the Fermi surface nesting occurs when more than 1/3 electron per Gd is doped, resulting in the failure to obtain a stable ferromagnetic (FM) state. More interestingly, GdI3 with appropriate Mg/Ca doping (1/6 Mg/Ca per Gd) turns to be half-metallic FM state. This AFM-FM transition results from the transfer of doped electrons to the spatially expanded Gd-5d orbital, which leads to the FM coupling of local half-full Gd-4f electrons through 5d-4f hybridization. Moreover, the shortened Gd-Gd length is the key to the formation of the stable ferromagnetic coupling. Our method provides new insights into obtaining stable FM materials from AFM materials.Comment: 16 pages, 6 figure

Laser-induced ultrafast spin injection in all-semiconductor magnetic CrI3/WSe2 heterobilayer

Spin injection stands out as a crucial method employed for initializing, manipulating, and measuring the spin state of electrons, which are fundamental to the creation of qubits in quantum computing. However, ensuring efficient spin injection while maintaining compatibility with standard semiconductor processing techniques is a significant challenge. Herein, we demonstrate the capability of inducing an ultrafast spin injection into a WSe2 layer from a magnetic CrI3 layer on a femtosecond time scale, achieved through real-time time-dependent density functional theory calculations upon a laser pulse. Following the peak of the magnetic moment in the CrI3 sublayer, the magnetic moment of the WSe2 layer reaches a maximum of 0.89 μB (per unit cell containing 4 WSe2 and 1 CrI3 units). During the spin dynamic, spin-polarized excited electrons transfer from the WSe2 layer to the CrI3 layer via a type-II band alignment. The large spin splitting in conduction bands and the difference in the number of spin-polarized local unoccupied states available in the CrI3 layer lead to a net spin in the WSe2 layer. Furthermore, we confirmed that the number of empty states, the spin-flip process, and the laser pulse parameters play important roles during the spin injection process. This work highlights the dynamic and rapid nature of spin manipulation in layered all-semiconductor systems, offering significant implications for the development and enhancement of quantum information processing technologies

Quasi-Epitaxial Growth of Magnetic Nanostructures on 4H-Au Nanoribbons

Phase engineering of nanomaterials is an effective strategy to tune the physicochemical properties of nanomaterials for various promising applications. Herein, by using the 4H-Au nanoribbons as templates, four novel magnetic nanostructures, namely 4H-Au @ 14H-Co nanobranches, 4H-Au @ 14H-Co nanoribbons, 4H-Au @ 2H-Co nanoribbons, and 4H-Au @ 2H-Ni nanoribbons, are synthesized based on the quasi-epitaxial growth. Different from the conventional epitaxial growth of metal nanomaterials, the obtained Co and Ni nanostructures possess different crystal phases from the Au template. Due to the large lattice mismatch between Au and the grown metals (i.e., Co and Ni), ordered misfit dislocations are generated at the Co/Au and Ni/Au interfaces. Notably, a new super-structure of Co is formed, denoted as 14H. Both 4H-Au @ 14H-Co nanobranches and nanoribbons are ferromagnetic at room temperature, showing similar Curie temperature. However, their magnetic behaviors exhibit distinct temperature dependence, resulting from the competition between spin and volume fluctuations as well as the unique geometry. This work paves the way to the templated synthesis of nanomaterials with unconventional crystal phases for the exploration of phase-dependent properties