Superconductivity in the intermetallic compound YRhAl

The intermetallic compound, YRhAl, has been prepared and is found to be isomorphic with RRhAl (R=Pr, Nd, Gd, Ho and Tm) compounds crystallizing in the orthorhombic TiNiSi-type structure (space group Pnma). Heat capacity and electrical resistivity measurements in the He-3 temperature range reveal that this compound is superconducting with a transition temperature, T_c, of 0.9 K. The electronic specific heat coefficient, γ, and the Debye temperature are found to be 6.1 mJ/mol K and 197 K, respectively. The specific heat jump at the superconducting transition is found to be consistent with the BCS weak-coupling limit. This combined with the earlier observation of superconductivity in LaRhAl (T_c=2.4 K) having a different structure than that of YRhAl, suggests that the underlying structure is not very crucial for the occurrence of superconductivity in RRhAl series of compounds.     

The role of the pion pair term in the theory of the weak axial meson exchange currents

The structure of the weak axial pion exchange current is discussed in various models. It is shown how the interplay of the chiral invariance and the double-counting problem restricts uniquely the form of the pion potential term, to the case when the nuclear dynamics is described by the Schrödinger equation with static nucleon-nucleon potential.     

Magneto-optical spectroscopy of Yb ions in huntite structure

We report the first measurements of magnetic circular dichroism (MCD) and magneto-optical activity (ratio of zero moments of MCD and absorption bands) of Yb³⁺ ion in the trigonal single crystals Yb_xTm_1−xAl₃(BO₃)₄ as a function of temperature in the range of 100-293 K. Magneto-optical activity follows the Curie-Weiss law with the Weiss constant θ=−55 K for Yb_0.1Tm_0.9Al₃(BO₃)₄ crystal. The value and origin of the magneto-optical activity is theoretically analyzed.     

Magnetic properties of xNi0.53Cu0.12Zn0.35Fe1.88O4+(1−x)BaTiO3 nanocomposites

The nanocrystalline Ni_0.53Cu_0.12Zn_0.35Fe_1.88O₄ and BaTiO₃ powders were prepared using Microwave-Hydrothermal (M-H) method at 160 °C/45 min. The as synthesized powders were characterized using the X-ray diffraction (XRD) and Transmission Electron Microscope (TEM). The size of the powders that were synthesized using M-H system was found to be ∼30 and ∼50 nm for ferrite phase and ferroelectric phases, respectively. The powders were densified using microwave sintering method at 900 °C/30 min. The ferrite and ferroelectric phases were observed from XRD and morphology of the composites was observed with the Scanning Electron Microscope (SEM).The magnetic hysteresis loops were recorded using the Vibrating Sample Magnetometer (VSM).The frequency dependence of real (μ′) and imaginary (μ″) parts of permeability was measured in the range of 1 MHz-1.8 GHz. The permeability decreases with an increase of BaTiO₃ content at 1 MHz. The transition temperature (T_C) of ferrite was found to be 245 °C. The T_C of composite materials decreases with an increase in BaTiO₃ content.     

Electrochromic properties of nano-composite nickel oxide film

In this study, we develop a nano-composite nickel oxide (NNO) film on the indium tin oxide (ITO)-coated glass substrate for electrochromic applications. The NNO film is composed of the core-shell structure of NiO/conducting ITO nano-particles. High porosity in the NNO film offers large active surface area for redox reaction. Electrochromic electrodes fabricated with the NNO films produce high transmittance variation (66.2% at a wavelength of 550 nm), fast switching speed (coloring: 3.5 s; bleaching: 4 s) and good durability, which are much better than those of ones made with the traditional nickel oxide films. The structure, morphology, and electrochromic properties are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and UV-vis spectroscopy.     

Analysis of force characteristics of a superconducting ball in a given magnetic field

The electromagnetic force characteristics along Z direction of a superconducting ball levitated by spherical coils with shaping blocks are calculated based on a semi-analytical method. The calculating results from the semi-analytical method are compared with the finite element analysis (FEA) method through a calculation example. The method can be applied to further analysis of dynamic characteristics and parameter optimization in the suspension system.     

Optical reflectance of blue bronze crystals near the Peierls transition

We report on the reflectance of blue bronze crystals in the visible frequency range as a function of temperature. The observed large oscillations in the reflectance at all wavelengths at temperatures near the Peierls transition are interpreted as interference effects stemming from a surface layer. It is found that the surface layer, which appears to be tied to fluctuations, can be as much as 1.6 microns thick.     

Study on the growth and interfacial strain of CoFe2O4/BaTiO3 bilayer films

CoFe₂O₄/BaTiO₃ bilayer films were epitaxially deposited on SrTiO₃ substrates by laser molecular beam epitaxy (LMBE). The growth process of the bilayer films was in-situ monitored by reflection high-energy electron diffraction (RHEED). Sixty nanometer thick-BTO layer was firstly fabricated in a layer-by-layer growth mode with an atomic smooth surface. CFO films with a varying thickness ranging from 5 to 60 nm were subsequently deposited on BTO-coated STO substrates. The different growth behaviors of CFO films were observed due to the lattice mismatch strain. Between two short stages of the growth mode transforming, a long duration with Stransky and Krastonov growth mode was maintained. Strainfully relaxed CFO film in the island growth mode was finally formed. High-resolution X-ray diffraction (HRXRD) was used to further analyze the strain effect. It was found that the tensile stress imposed on BTO by CFO was strengthened with increasing the thickness of CFO films, which could lessen the distortion of BTO by counteracting the compressive stress caused by STO substrates. The strengthened tensile stress weakened the ferroelectric property of BTO films by reducing structural tetragonality, which was demonstrated by polarization-electric (P-E) measurement.