Spintronic properties of the Ti2CoB Heusler compound by density functional theory

The electronic structure and magnetic properties of the Ti₂CoB Heusler compound with a high-ordered CuHg₂Ti structure were investigated using the self-consistent full potential linearized augmented plane wave (FPLAPW) method within the density functional theory (DFT). Spin-polarized calculations show that the Ti₂CoB compound is half-metallic ferromagnetic with a magnetic moment of 2 μ_B at the equilibrium lattice constant, a=5.74 Å. The Ti₂CoB Heusler compound is ferromagnetic below the equilibrium lattice constant and ferrimagnetic above the equilibrium lattice constant. A large peak in majority-spin DOS and an energy gap in minority-spin DOS are observed at the Fermi level, yielding a spin polarization of 100%. A spin polarization higher than 90% is achieved for a wide range of lattice constants between 5.6 and 6.0 Å.     

Buckling delamination of a sandwich plate-strip with piezoelectric face and elastic core layers

In this study, the buckling delamination problem of a sandwich plate-strip with a piezoelectric face and elastic core layers is studied. It is assumed that the plate-strip is simply supported and grounded along its two parallel ends and is subjected to uniformly-distributed compressive forces on these ends. Moreover, we suppose that the plate-strip has two interface inner cracks between the face and the core layers and it is also supposed that before the plate-strip is loaded (i.e. in the natural state), the surfaces of these cracks have insignificant initial imperfections. Due to compressive forces acting along the cracks we investigate the evolution of the initial imperfections of the cracks’ surfaces. Hence, the values of the critical buckling delamination force of the considered plate-strip are determined from the criteria, according to which, the considered initial imperfections of the cracks’ surfaces grow indefinitely by the compressive forces. Mathematical modeling of the considered problem is formulated within the scope of the exact nonlinear equations of electro-elasticity in the framework of the piecewise homogeneous body model, the solution of which is found numerically by employing the finite elements method. Numerical results showing the influences of the geometrical and material parameters as well as the coupling of the electrical and mechanical fields on the values of the critical force are presented and analyzed.     

Darzens reaction of acyl phosphonates with alpha-bromo ketones: selective synthesis of cis- and trans-epoxyphosphonates

Acyl phosphonates with alpha-halo ketones in the presence of bases at room temperature afford cis- and trans-epoxyphosphonates in good chemical yields and high selectivities using different bases. The diastereoselectivity of this reaction is easily controlled by changing the base. Changing the base from Cs2CO3 to DBU changed the diastereomeric ratio (trans/cis) from 3/2 to 9/1. Moreover, the treatment of the trans isomer with DBU showed a complete conversion to the corresponding cis isomer.     

Magnetic properties of R3Co29Si4B10 (R=La, Ce, Pr, Nd, Sm, Gd and Dy) borides

The crystal structure and magnetic properties of quaternary rare-earth intermetallic borides R₃Co₂₉Si₄B₁₀ with R=La, Ce, Pr, Nd, Sm, Gd and Dy have been studied by X-ray powder diffraction and magnetization measurements. All compounds crystallize in a tetragonal crystal structure with the space group P4/nmm. Compounds with R=La, Ce, Pr, Nd and Sm are ferromagnets, while ferrimagnetic behavior is observed for R=Gd and Dy. The Curie temperatures vary between 149 K and 210 K. The Curie temperatures in R₃Co₂₉Si₄B₁₀ (R=Ce, Pr, Nd, Sm, Gd, Dy) compounds are roughly proportional to the de Gennes factors.     

New rhodamine nitroxide based fluorescent probes for intracellular hydroxyl radical identification in living cells

The synthesis, characteristics, and biological applications of a series of new rhodamine nitroxide fluorescent probes that enable imaging of hydroxyl radicals (?OH) in living cells are described. These probes are highly selective for ?OH in aqueous solution, avoiding interference from other reactive oxygen species (ROS), and they facilitate ?OH imaging in biologically active samples. The robust nature of these probes (high specificity and selectivity, and facile synthesis) offer distinct advantages over previous methods for ?OH detection.     

Magnetic properties of the Pr1−xGdxCo4B compounds

In this work, we have investigated the effect of the substitution of Gd for Pr on the crystal structure and magnetic properties of the Pr_1−xGd_xCo₄B compounds for 0?x?1 using X-ray powder diffraction, magnetic measurements, and differential scanning calorimetry (DSC). These compounds have hexagonal CeCo₄B-type structure with the space group P6/mmm. The substitution of Gd for Pr leads to a decrease of the unit-cell parameters a and the unit-cell volume V, while the unit-cell parameter c increases slightly. Magnetic measurements indicate that all samples are ordered magnetically below room temperature. The Curie temperatures determined by DSC technique increase as Pr is substituted by Gd. The saturation magnetization at 5 K decreases upon Gd substitution up to x=0.6, and then increases again.     

A first-principle study of half-metallic ferrimagnetism in the Ti2CoGa Heusler compound

Electronic structure calculations based on density functional (DFT) theory within the generalized gradient approximation (GGA) for the Ti₂CoGa Heusler compound have been performed using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method. The electronic band structures and density of states of the Ti₂CoGa compound show that the spin-up electrons are metallic, but the spin-down bands have a gap of 0.5 eV, resulting in stable half-metallic ferrimagnetic behavior with a magnetic moment of 2μ_B.     

Influence of Ho substitution for Nd on magnetic properties of the Nd1−xHoxMn2Ge2 germanides

The structure and magnetic properties of Nd_1−xHo_xMn₂Ge₂ (0.0≤x≤1.0) germanides were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) techniques and AC magnetic susceptibility measurements. All compounds crystallize in the ThCr₂Si₂-type structure with the space group I4/mmm. Substitution of Ho for Nd leads to a linear decrease in the lattice constants and the unit cell volume, and the magnetic interactions in the Mn sublattice cross over from a ferromagnetic character to an antiferromagnetic one. A typical SmMn₂Ge₂-like behavior is observed for x=0.6 and 0.8. The results are collected in a phase diagram.     

Half-metallic ferrimagnetism in the Ti2CoAl Heusler compound

Density functional calculations performed on the Ti₂CoAl Heusler compound confirm it to be a half-metallic ferrimagnet with the spin-down energy gap of 0.49 eV. The Ti₂CoAl Heusler compound has a magnetic moment of 2 μ_B at the equilibrium lattice constant a=6.14 Å. The Ti₂CoAl Heusler compound is ferrimagnetic and maintains the half-metallic character having 100% polarization for lattice constants ranging between 5.85 and 6.44 Å.