Giant magnetic anisotropy of a two-dimensional metal-dicyanoanthracene framework

Transition-Metal Interlink Neural Network: Machine Learning of 2D Metal-Organic Frameworks with High Magnetic Anisotropy

Two-dimensional (2D) metal-organic framework (MOF) materials with large perpendicular magnetic anisotropy energy (MAE) are important candidates for high-density magnetic storage. The MAE-targeted high-throughput screening of 2D MOFs is currently limited by the time-consuming electronic structure calculations. In this study, a machine learning model, namely, transition-metal interlink neural network (TMINN) based on a database with 1440 2D MOF materials is developed to quickly and accurately predict MAE. The well-trained TMINN model for MAE successfully captures the general correlation between the geometrical configurations and the MAEs. We explore the MAEs of 2583 other 2D MOFs using our trained TMINN model. From these two databases, we obtain 11 unreported 2D ferromagnetic MOFs with MAEs over 35 meV/atom, which are further demonstrated by the high-level density functional theory calculations. Such results show good performance of the extrapolation predictions of TMINN. We also propose some simple design rules to acquire 2D MOFs with large MAEs by building a Pearson correlation coefficient map between various geometrical descriptors and MAE. Our developed TMINN model provides a powerful tool for high-throughput screening and intentional design of 2D magnetic MOFs with large MAE.

Two-dimensional group-III nitrides and devices: a critical review

As third-generation semiconductors, group-III nitrides are promising for high power electronic and optoelectronic devices because of their wide bandgap, high electron saturation mobility, and other unique properties. Inspired by the thickness-dependent properties of two-dimensional (2D) materials represented by graphene, it is predicted that the 2D counterparts of group-III nitrides would have similar properties. However, the preparation of 2D group-III nitride-based materials and devices is limited by the large lattice mismatch in heteroepitaxy and the low rate of lateral migration, as well as the unsaturated dangling bonds on the surfaces of group-III nitrides. The present review focuses on theoretical and experimental studies on 2D group-III nitride materials and devices. Various properties of 2D group-III nitrides determined using simulations and theoretical calculations are outlined. Moreover, the breakthroughs in their synthesis methods and their underlying physical mechanisms are detailed. Furthermore, devices based on 2D group-III nitrides are discussed accordingly. Based on recent progress, the prospect for the further development of the 2D group-III nitride materials and devices is speculated. This review provides a comprehensive understanding of 2D group-III nitride materials, aiming to promote the further development of the related fields of nano-electronic and nano-optoelectronics.

Emergence of magnetic anisotropy by surface adsorption of transition metal dimers on γ-graphyne framework

In this paper a systematic study is carried out to demonstrate the structural stability and magnetic novelty of adsorbing transition metal (TM) dimers (A-B) on graphyne (GY) surface, GY@A-B. Our research points out that the dimers are strongly adsorbed onto GY due to their large natural pores and the electron affinity of the sp-hybridized carbon atoms. Electronic properties of these dimer-graphyne composite systems are of particular importance as they behave as degenerate semiconductors with partial occupation of states atE_F. Furthermore, their remarkable spin polarization (>80%) at Fermi energy (E_F) can be of paramount importance in spintronics applications. Most of the GY@A-B structures exhibit large magnetic anisotropies as well as magnetic moments along the out-of-plane direction with respect to the GY surface. Particularly, GY@Co-Ir, GY@Ir-Ir and GY@Ir-Os structures possess positive magnetic anisotropic energies (MAE) of 121 meV, 81 meV and 137 meV, respectively, which are comparable to other well-known TM dimer doped systems. The emergence of high MAE can be understood using the second-order perturbation theory on the basis of the strong spin-orbit coupling (SOC) between the two TMs and the degeneracy of their d-orbitals nearE_F. A close correspondence between the simulated and the analytical results has been established through our work. Further, a simple estimation shows that, GY@A-B structures have the potential to store data up to 64 PB m^-2. These intriguing electronic characteristics along with magnetism suggest GY@A-B to be a promising material for future magnetic storage devices.

Robust spin manipulation in 2D organometallic Kagome lattices: a first-principles study

The search for 2D ferromagnets with versatile magneto-electronic properties is becoming more active due to their potential applications in spintronic devices. To screen out the optimal compositions, we have explored a series of two-dimensional M3C12X12 (M = 5d transition metals, and X = S, NH, and O) metal-organic frameworks with Kagome lattice patterns through first-principles calculations. By varying the metal center and ligand functional radicals, both the electronic and spin-related properties can be easily tuned to meet the requirements for multifunctional applications in spintronic devices. Among them, Re3C12N12H12 is identified to be a ferromagnetic bipolar magnetic semiconductor with the highest Curie temperature (TC > 330 K). Re3C12O12 is found to be an ideal half-metal with a spin gap of 0.97 eV, which is beneficial for use as a spin-filter. Meanwhile, both Re3C12N12H12 and Re3C12O12 exhibit considerable out-of-plane magnetic anisotropy energies (>26 meV per atom), which benefit the spintronic applications. The theoretical results not only show that the 2D organometallic Kagome lattice is a good platform for designing spintronic materials, but also provides a feasible way to realize robust spin manipulation.