Singlet two-electron states in superconducting materials based on iron pnictides

Two-electron states with a zero pulse for the symmetry group of superconducting materials based on iron pnictides are considered. Cases are established for the introduction of one or two additional quantum numbers, notably, the internal quantum number, which characterizes single-electron states, or an additional quantum number, i.e. the irreducible representation index of the intermediate group. The octet structure of zeros observed in photoelectron spectra and the phase difference between the two-electron states on various Fermi surfaces are interpreted.     

EPR and optical spectroscopy of impurities in two synthetic beryls

Two synthetic beryls (Al₂Be₃Si₆O₁₈) of different color (purple and blue-green) were studied with electron paramagnetic resonance (EPR) and optical spectroscopy. In both crystals, the known spectra of Cu²⁺ and Fe³⁺ were observed with the same relative intensity. In the purple sample heated at 700°C in hydrogen atmosphere, two different kinds of Mn²⁺ EPR spectra were observed. The main one is pseudoaxial, it arises from ions substituted for Al³⁺ at position 4c of the structure. The weaker one is more complex, it has orthorhombic symmetry and is characterized by an unusually large zero-field splitting (B ₂⁰ = 741 · 10⁻⁴ cm⁻¹) and an isotropic hyperfine constantA = 70 G. This spectrum arises from Mn²⁺ at position 6f in the structure, normally occupied by Be. From optics, the blue-green color arises from Cu²⁺, while the purple one is due to Mn³⁺.     

Domain Structure and Magnetization Reversal in Multilayer Structures Consisting of Thin Permalloy Films Separated with Nonmagnetic Interlayers

Russian Physics Journal - Using numerical micromagnetic modeling, we have investigated the development of domain structure and magnetization reversal in multilayer thin-film structures. The...     

Micromagnetic Analysis of Edge Effects in a Thin Magnetic Film during Local Excitation of Magnetization Oscillations

Russian Physics Journal - The method of numerical micromagnetic simulation was used to study the magnetization dynamics of a thin film with uniaxial magnetic anisotropy during ferromagnetic...     

Heat capacity of GdBiGeO<Subscript>5</Subscript> in the temperature range 373–1000 K

Ternary oxide GdBiGeO₅ was synthesized by a ceramic method. The heat capacity of crystalline gadolinium bismuth germanate as a function of temperature in the range 373–1000 K has been studied by differential scanning calorimetry. It has been demonstrated that the temperature dependence of the heat capacity can be described by the classical Maier–Kelley equation. From the experimental C _P = f(T) data, the thermodynamic functions (the change in enthalpy and entropy) of ternary oxide GdBiGeO₅ have been calculated.     

Specific features of magnetoacoustic waves in Fe<Subscript>3</Subscript>BO<Subscript>6</Subscript>

The specific features of magnetoacoustic waves propagating in an orthorhombic antiferromagnet with weak ferromagnetism, namely, the Fe₃BO₆ orthoborate, are investigated experimentally in the vicinity of the spontaneous, first-order orientational phase transition. It is revealed that, at the phase transition point, the amplitude of active acoustic waves interacting with spin waves increases significantly. A phenomenological theory of magnetoelastic waves in orthoferrites is proposed. This theory allows for an intermediate domain structure existing in the range of a first-order orientational phase transition and offers a satisfactory explanation of the experimentally observed anomaly in the amplitude of active acoustic waves.     

High-temperature heat capacity and thermodynamic properties of Pb<Subscript>4</Subscript>V<Subscript>2</Subscript>O<Subscript>9</Subscript> and Pb<Subscript>8</Subscript>V<Subscript>2</Subscript>O<Subscript>13</Subscript>

The molar heat capacity of Pb₄V₂O₉ and Pb₈V₂O₁₃ in the temperature range 350–1000 K was measured by differential scanning calorimetry. It was determined that the plot C_p = f(T) for Pb₈V₂O₁₃ has an extremum within the range 416–516 K, which is due to a phase transition. A correlation was found between the heat capacity and composition of oxides in the PbO–V₂O₅ system. The data obtained allowed one to predict the specific heat capacity value for Pb(VO₃)₂.     

Synthesis and properties of magnetic semiconductor InSb〈Mn,Cd〉

Polycrystalline indium antimonide samples codoped with manganese (0.8–1 at %) and cadmium (3.9 at %) are prepared by quenching from melt. Despite the high contents of these dopants, only InSb maxima are observed in X-ray diffraction patterns of these samples. As probed by magnetic studies, the samples are ferrimagnets having Curie points of about 577 K and room-temperature specific magnetizations of σ ≈ 0.5 G cm³/g (H = 6 kOe). We suggest that the magnetic properties of the samples are dictated by InSb〈Mn,Cd〉 microinclusions, which are located in grain boundaries and dislocations.