AB INITIO CALCULATION OF ADSORPTION POSITION EFFECT ON MAGNETIZATION REDISTRIBUTION IN P-DOPED SILICENE

The behavior (substitution and adsorption) of a phosphorus atom on the surface of silicene is studied using quantum mechanical calculations. The most favorable positions, binding energy and activation of the phosphorus diffusion barrier have been established. The change in the local magnetic moment of the phosphorus atom is described depending on its position and the position of the surrounding silicon elements.

Impact of Disorder on Properties of Vacancies: A Case Study of B2 and A2 Polymorphs of Non-Stoichiometric Fe2CoAl

We have performed an ab initio study of vacancy-induced changes in thermodynamic, structural and magnetic properties of single-phase ferromagnetic Fe2CoAl with a chemically disordered (i) two-sublattice B2 phase or (ii) single-sublattice A2 phase. The two polymorphs of slightly non-stoichiometric Fe2CoAl (Fe27Co14Al13) were modeled by two different 54-atom supercells with atoms distributed according to the special quasi-random structure (SQS) concept. Both the lower-energy B2 phase and a higher-energy A2 phase possess elastic constants that correspond to an auxetic material that is mechanically stable. The properties of vacancies were computed by systematically removing different atoms (one at a time) from the supercells and quite wide ranges of values of vacancy-related characteristics were obtained. The increase in the level of disorder (when changing from the B2 to the A2 phase) results in an increase in the scatter of calculated values. The Fe and Co vacancies have lower vacancy formation energies than the Al ones. The total magnetic moment of the supercell decreases when introducing Fe and Co vacancies but it increases due to Al ones. The latter findings can be partly explained by an increase of the local magnetic moment of Fe atoms when the number of Al atoms in the first neighbor shell of Fe atoms is reduced, such as due to Al vacancies.

Crystal Structure and Magnetism of Potassium-Intercalated 2,7-Dimethylnaphthalene

The rich physical properties of metal-intercalated polycyclic aromatic hydrocarbon materials have recently attracted considerable attention. Crystals of potassium-intercalated 2,7-dimethylnaphthalene were synthesized via solid phase reaction. The combination of XRD measurements and first-principles calculations indicated that each unit cell contains two potassium atoms and four organic molecules. Magnetization measurements revealed that the samples show a Curie paramagnetism. Theoretical calculations showed that the intercalated structure becomes metallic and has local magnetic moment. Raman spectroscopy confirmed the migration of electron from potassium 4s to carbon 2p orbital, which is the source of magnetism. Our research on naphthalene derivatives is helpful for expanding the range of novel organic magnetic materials and organic superconducting materials.

Induced Magnetism in Non-metal Doped CdS Monolayer

The structural, electronic, and magnetic properties of CdS monolayer doped with non-metallic (NM) atoms B, C and N are studied based on ab initio density functional theory calculations within the generalized gradient approximation as revised for solids by Perdew, Burke and Ernzerhof (PBE-sol). The total magnetic moments per supercell of B, C and N-doped CdS monolayer is found to be ~1.0 µB, ~2.0 µB and ~1.0 µB respectively. As the electronegativity of the dopant increases, the local magnetic moment tends to localize and 2p-states of the dopants gradually move towards the valence band maximum of the host CdS. Our study also confirmed that the introduction of impurity atom by substitution of S atom results in half-metallic magnetism. Our investigation concludes that doping of NM element is an efficient way of altering the magnetic and electronic properties in CdS monolayer.

Quantum mechanical modelling of phosphorus qubits in silicene under constrained magnetization

The dependent behaviour of a pair of phosphorus atoms in silicene was shown by a DFT calculation with constrained magnetization. The total energy and charge distribution change with the rotation of the local magnetic moment of the P atoms.

Insight into the magnetic moment of iron borides: theoretical consideration from the local coordinative and electronic environment

Linear relationships between the local magnetic moment of iron borides and the bond valence as well as the orbital energy were disclosed.

Reciprocity between local moments and collective magnetic excitations in the phase diagram of BaFe2(As1−xPx)2

Unconventional superconductivity arises at the border between the strong coupling regime with local magnetic moments and the weak coupling regime with itinerant electrons, and stems from the physics of criticality that dissects the two. Unveiling the nature of the quasiparticles close to quantum criticality is fundamental to understand the phase diagram of quantum materials. Here, using resonant inelastic x-ray scattering (RIXS) and $${\rm{Fe}}-{{\rm{K}}}_{\beta }$$ Fe − K β emission spectroscopy (XES), we visualize the coexistence and evolution of local magnetic moments and collective spin excitations across the superconducting dome in isovalently-doped BaFe$${}_{2}$$ 2 (As$${}_{1-x}$$ 1 − x P$${}_{x}$$ x )$${}_{2}$$ 2 (0.00 $$ \le $$ ≤ x $$\le 0.52$$ ≤ 0.52 ). Collective magnetic excitations resolved by RIXS are gradually hardened, whereas XES reveals a strong suppression of the local magnetic moment upon doping. This relationship is captured by an intermediate coupling theory, explicitly accounting for the partially localized and itinerant nature of the electrons in Fe pnictides. Finally, our work identifies a local-itinerant spin fluctuations channel through which the local moments transfer spin excitations to the particle-hole (paramagnons) continuum across the superconducting dome.

Elastic Parameters of Paramagnetic Fe–20Cr–20Ni-Based Alloys: A First-Principles Study

The single-crystal and polycrystalline elastic parameters of paramagnetic Fe0.6−xCr0.2Ni0.2Mx (M = Al, Co, Cu, Mo, Nb, Ti, V, and W; 0 ≤ x ≤ 0.08) alloys in the face-centered cubic (fcc) phase were derived by first-principles electronic structure calculations using the exact muffin-tin orbitals method. The disordered local magnetic moment approach was used to model the paramagnetic phase. The theoretical elastic parameters of the present Fe–Cr–Ni-based random alloys agree with the available experimental data. In general, we found that all alloying elements have a significant effect on the elastic properties of Fe–Cr–Ni alloy, and the most significant effect was found for Co. A correlation between the tetragonal shear elastic constant C′ and the structural energy difference ΔE between fcc and bcc lattices was demonstrated. For all alloys, small changes in the Poisson’s ratio were obtained. We investigated the brittle/ductile transitions formulated by the Pugh ratio. We demonstrate that Al, Cu, Mo, Nb, Ti, V, and W dopants enhance the ductility of the Fe–Cr–Ni system, while Co reduces it. The present theoretical data can be used as a starting point for modeling the mechanical properties of austenitic stainless steels at low temperatures.