Structure and magnetic properties of icosahedral PdxAg13-x (x = 0-13) clusters.

In this article, we present a modified Velocity-Verlet algorithm that makes cluster system converge rapidly and accurately. By combining it with molecular dynamics simulations, we develop an effective global sampling method for extracting isomers of bimetallic clusters. Using this method, we obtain the isomers of icosahedral PdxAg13-x (x = 0-13). Additionally, using the first-principle spin-polarized density functional theory approach, we find that each isomer still retains its icosahedral structure because of strong s-d orbital hybridization, and the cluster is more stable when a Pd atom is at the center of the cluster. With increasing x value, the magnetic moment decreases linearly from 5.0 µB at x = 0, until reaching zero at x = 5, and then increases linearly up to 8.0 µB at x = 13. By calculating the atom-projected density of states (PDOS), we reveal that the magnetic moment of PdxAg13-x mainly originates from s electrons of Ag when 0 ≤ x < 5, and d electrons of Pd when 5 < x ≤ 13. The PDOS results also show that the PdxAg13-x tends to transform from a semiconductor state to semi-metallic state when x gradually increases from 0 to 13.

Electric field control of the magnetic anisotropy energy of double-vacancy graphene decorated by iridium atoms.

To solve the fundamental dilemma in data storage applications, it is crucial to manipulate the magnetic anisotropy energy (MAE). Herein, using first-principles calculations, we predict that the system of double-vacancy graphene decorated by iridium atoms possesses high stability, giant MAE, perpendicular-anisotropy and long-range ferromagnetic coupling. More importantly, the amplitude of MAE can be manipulated by electric fields. This is due to the change in the occupation number of Ir-5d orbitals. The present hybrid system could be a high-performance nanoscale information storage device with ultralow energy consumption.

High-temperature quantum anomalous Hall effect in honeycomb bilayer consisting of Au atoms and single-vacancy graphene.

The quantum anomalous Hall effect (QAHE) is predicted to be realized at high temperature in a honeycomb bilayer consisting of Au atoms and single-vacancy graphene (Au2-SVG) based on the first-principles calculations. We demonstrate that the ferromagnetic state in the Au2-SVG can be maintained up to 380 K. The combination of spatial inversion symmetry and the strong SOC introduced by the Au atoms causes a topologically nontrivial band gap as large as 36 meV and a QAHE state with Chern number C = -2. The analysis of the binding energy proved that the honeycomb bilayer is stable and feasible to be fabricated in experiment. The QAHEs in Ta2-SVG and other TM2-SVGs are also discussed.

Reversible switching of magnetic states by electric fields in nitrogenized-divacancies graphene decorated by tungsten atoms.

Magnetic graphene-based materials have shown great potential for developing high-performance electronic devices at sub-nanometer such as spintronic data storage units. However, a significant reduction of power consumption and great improvement of structural stability are needed before they can be used for actual applications. Based on the first-principles calculations, here we demonstrate that the interaction between tungsten atoms and nitrogenized-divacancies (NDVs) in the hybrid W@NDV-graphene can lead to high stability and large magnetic anisotropy energy (MAE). More importantly, reversible switching between different magnetic states can be implemented by tuning the MAE under different electric fields, and very low energy is consumed during the switching. Such controllable switching of magnetic states is ascribed to the competition between the tensile stain and orbital magnetic anisotropy, which originates from the change in the occupation number of W-5d orbitals under the electric fields. Our results provide a promising avenue for developing high-density magnetic storage units or multi-state logical switching devices with ultralow power at sub-nanometer.

First-principles prediction of magnetic superatoms in 4d-transition-metal-doped magnesium clusters.

We theoretically predict magnetic superatoms in the 4d-transition-metal-doped Mg8 clusters using a spin-polarized density functional theory method. We demonstrate that TcMg8 is highly energetically stable in both structure and magnetic states, and identify it as a magnetic superatom with a magnetic moment as large as 5 µB. The magnetic TcMg8 with 23 valence electrons has a configuration of 1S(2)1P(6)1D(10) closed shell and 2S(1)2D(4) open shell, complying with Hund's rule similar to the single atom. We elucidate the formation mechanism of the magnetic TcMg8 superatom based on the detailed analysis of molecular orbitals, and attribute it to the large exchange interaction and moderate crystal field effect. Finally, we predict that the magnetic TcMg8 may exhibit semiconductor-like property with spin polarization characteristics.

Giant magnetic moment of the core-shell Co13@Mn20 clusters: first-principles calculations.

The core-shell clusters Co(13)@TM(20) with TM = Mn, Fe, Co, and Ni are investigated within first-principles simulations in the framework of density-functional theory. Huge magnetic moments have been found in the Co(13)@TM(20) clusters especially for the Co(13)@Mn(20) cluster with a giant magnetic moment of 113 µ(B). The large magnetic moments are mainly due to the special core-shell structure and the weak interaction between the TM and other atoms.