Structural and magnetic properties of CeZnAl_3 single crystals

We have synthesized single crystals of CeZnAl_3,which is a new member of family of Ce-based intermetallics CeTX_3(T=transition metal, X=Si, Ge, Al), crystallizing in the non-centrosymmetric tetragonal BaNiSn_3-type structure. Magnetization,specific heat and resistivity measurements all show that CeZnAl_3 orders magnetically below around 4.4 K. Furthermore,magnetization measurements exhibit a hysteresis loop at low temperatures and fields, indicating the presence of a ferromagnetic component in the magnetic state. This points to a different nature of the magnetism in CeZnAl_3 compared to the other isostructural CeTAl_3 compounds. Resistivity measurements under pressures up to 1.8 GPa show a moderate suppression of the ordering temperature with pressure, suggesting that measurements to higher pressures are required to look for quantum critical behavior.     

Low-temperature magnetic properties of HoMn0.5Co0.5O3 single crystals

The magnetic behavior of a HoMn_0.5Co_0.5O₃ single crystal grown by electrochemical deposition was studied by measuring magnetization in the temperature range 5–300 K in magnetic fields of up to 50 kOe. The results obtained are treated within a model of the two-phase magnetic state of a crystal. A comparative analysis of the magnetic properties of HoMn_0.5Co_0.5O₃ and LaMn_0.5Co_0.5O₃ single crystals was carried out.     

Use of the kerr magnetooptical effect to study the magnetic properties of hematite single crystals

The hysteresis loops of natural single crystals of hematite have been observed on an oscilloscope by means of the Kerr magnetooptical effect. Powder patterns are shown illustrating the remagnetization. The orientation of the ferromagnetic moment is extremely sensitive to internal stresses in the crystal.     

Temperature dependence of the lattice parameters and magnetic properties of Er3Ir single crystals

Er₃Ir single crystals were grown by the Czochralski method from a levitated melt. The electrical resistivity thermal dependence exhibits ordering temperature of the erbium sublattice at 40 K and a spin reorientation process at 22 K. The DC and AC magnetic susceptibility show antiferromagnetic ordering in the form of an asymmetric peak. The magnetization in strong magnetic fields up to 140 kOe exhibits anisotropy. The lattice parameters’ thermal dependence of Er₃Ir and Er₃Ni show anisotropy and anomalous behaviour.     

Synthesis and magnetic properties of Cu3B2O6 single crystals

The temperature dependence of the magnetic susceptibility of Cu₃B₂O₆ single crystals grown by spontaneous crystallization from a melt consisting of a mixture of CuO and B₂O₃ and the behavior of their magnetization are investigated in magnetic fields up to 55 kOe. A broad susceptibility maximum is observed near 39 K, and a sharp drop in susceptibility is observed at T<10 K. The paramagnetic Néel temperatures for all orientations of the magnetic field in the crystal investigated are negative, attesting to the predominantly antiferromagnetic character of the exchange interactions. The effective magnetic moment of the Cu²⁺ ion is anisotropic and lies in the range from 1.054μ _B to 1.545μ _B. The magnetization depends linearly on magnetic field at T>10 K, whereas at temperatures below 10 K a discontinuity is observed at fields of the order of 40 kOe. At room temperature, electron magnetic resonance characterized by an almost isotropic g factor (g=2.165) is detected at 36.22 GHz. The exchange interactions in Cu₃B₂O₆ are analyzed on the basis of the Goodenough-Kanamori rules. The possibility of the establishment of a singlet magnetic state in the crystal is analyzed. Fiz. Tverd. Tela (St. Petersburg) 41, 677–679 (April 1999)     

Magnetic control of magnetic shape-memory single crystals

We present a phenomenological model for the magneto-mechanical evolution of shape-memory alloy single crystals. The existence of solutions for given magnetic field is commented and optimal control results are established.     

Scintillation properties of BeO single crystals

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 49, No. 2, pp. 286–291, August, 1988.     

Electrical properties of molybdenite single crystals

Molybdenite crystals used in the present work were grown by direct vapour transport or sublimation method. The electrical resistivities and I-V characteristics were measured at different temperatures in the symmetry plane. The room temperature resistance of a specimen annealed for different periods has also been measured. These results are described and discussed.     

Luminescent properties of LiCl-Cu single crystals

The absorption, photoluminescence, x-ray luminescence, and thermoluminescence spectra, and the photoluminescence excitation spectra of LiCl-Cu single crystals with different activator concentration were investigated at temperatures of 79–450°K. The absorption spectrum at room temperature has two bands with maxima at 237 and 259 nm. The absorption coefficient of the 237 nm band is proportional to the copper concentration in the crystal (C_Cu ≤ 7·10^?4 mole %). The photoluminescence and x-ray luminescence spectrum at room temperature consists of one emission band at 324 nm, which conforms with the Mollwo-Ivey rule in the homologous series RbCl → KCl → NaCl → LiCl. The copper ions create trapping levels for electrons and holes at different depths in the forbidden band of the LiCl crystal. The correlation between the thermoluminescence peaks and the recombination-luminescence excitation bands (infrared stimulation) is investigated.     

Surface properties of GaTe single crystals

Surface properties of gallium telluride were studied. It was found that the surface after vacuum cleavage is partly reconstructed from monoclinic to hexagonal. Peculiarities of the surface topology are also discussed.     

Optical properties of InBr single crystals

Single crystals of orthorhombic InBr were grown by the sublimation technique. Two of the three principal refractive indices were determined by measuring interference due to multiple reflection. The absorption curve near the band edge was measured at 295,80 and 10°K for different polarisation vectors of the incident light. At low temperatures large exciton absorptions could be seen which enabled us to determine accurate values of the band gap energy.     

Optical properties of Tm-doped GaSe single crystals

Optical properties of Tm-doped GaSe single crystals were investigated by measurements of optical absorption and photoluminescence. The single crystals were grown by the Bridgman technique. The X-ray diffraction analysis revealed that the single crystals were in the ε-type GaSe phase. The optical absorption spectra showed a sharp absorption peak at 582 nm near the band edge, which is due to direct free exciton. The temperature dependence of the energy of the exciton absorption peak was well fitted by the Varshni relation. In the photoluminescence spectrum at 10 K, we observed a very weak emission peak at 586 nm, a relatively strong emission peak centered at 613 nm, and several sharp and narrow emission peaks in the 790-840 nm region. The two emission peaks at 586 and 613 nm were associated with intrinsic emission lines due to direct free exciton and indirect bound exciton. The emission peaks in the 790-840 nm region, which were related to extrinsic emission, were assigned as due to the ³F₄→³H₆ transition of Tm³⁺ ions with a low symmetry of D₃ in the host lattice.     

Phonon properties of CoSb2 single crystals

The phonon properties of CoSb(2) have been investigated by Raman scattering spectroscopy and lattice dynamics calculations. Sixteen out of eighteen Raman active modes predicted by factor-group analysis are experimentally observed and assigned. The calculated and measured phonon energies at the Γ point are in very good agreement. The temperature dependence of the A(g) symmetry modes is well represented by phonon-phonon interactions without contribution from any other phonon or electron related interactions.     

Laser properties of praseodymium pentaphosphate single crystals

PrP₅O₁₄, Pr_xLa_1−xP₅O₁₄, and Pr_xY_1−xP₅O₁₄ (0≦x≦1) single crystals of laser quality were synthesized and their crystallographic and optical parameters measured. Laser emissions in the visible (λ=637.4 nm) with no mirrors in place (superradiance) and also in various optical resonators have been observed.     

Electrical transport properties of CuS single crystals

Electrical resistivity, transverse magnetoresistance and thermoelectric power measurements were performed on CuS high quality single crystals in the range 1.2-300 K and under fields of up to 16 T. The zero field resistivity data are well described below 55 K by a quasi-2D model, consistent with a carrier confinement at lower temperatures, before the transition to the superconducting state. The transverse magnetoresistance develops mainly below 30 K and attains values as large as 470% for a 16 T field at 5 K, this behaviour being ascribed to a band effect mechanism, with a possible magnetic field induced DOS change at the Fermi level. The transverse magnetoresistance shows no signs of saturation, following a power law with field Δρ/ρ(0) ∝ H(1.4), suggesting the existence of open orbits for carriers at the Fermi surface. The thermoelectric power shows an unusual temperature dependence, probably as a result of the complex band structure of CuS.     

Effects of different annealing atmospheres on magnetic properties in La2CoMnO6 single crystals

We have successfully synthesized the high-quality single crystals of double perovskite La₂CoMnO₆ by flux method and investigated the effects of different annealing conditions on the magnetic properties. In an as-grown crystal, ferromagnetic order along the c axis arises below 204 K, and the spin-glass-type behavior inherent from ionic disorders is also observed. Upon annealing in different gas environments, the reconstructed magnetic states induce a metamagnetic transition (after Ar annealing), and increase Curie temperature (after O₂ annealing). After quenching, the magnetic transition temperature decreases significantly, comprising lots of defects and disorders. Our results provide adequate procedures to control magnetic properties of double-perovskite compounds.     

Structural and magnetic properties of CeZnAl<Subscript>3</Subscript> single crystals

We have synthesized single crystals of CeZnAl₃, which is a new member of family of Ce-based intermetallics CeTX₃ (T=transition metal, X=Si, Ge, Al), crystallizing in the non-centrosymmetric tetragonal BaNiSn₃-type structure. Magnetization, specific heat and resistivity measurements all show that CeZnAl₃ orders magnetically below around 4.4 K. Furthermore, magnetization measurements exhibit a hysteresis loop at low temperatures and fields, indicating the presence of a ferromagnetic component in the magnetic state. This points to a different nature of the magnetism in CeZnAl₃ compared to the other isostructural CeTAl₃ compounds. Resistivity measurements under pressures up to 1.8 GPa show a moderate suppression of the ordering temperature with pressure, suggesting that measurements to higher pressures are required to look for quantum critical behavior.