Anisotropic magnetotransport and extremely large magnetoresistance in NbAs2 single crystals.

We report the extremely large magnetoresistance and anisotropic magnetoresistance in a non-magnetic semimetallic NbAs2 single crystal. Unsaturated transverse XMR with quadratic field dependence has been observed to be ~3 × 105 % at 2 K and 15 T. Up to 12.5 K, clear Shubnikov de Haas (SdH) quantum oscillations were observed from which two distinct Fermi pockets were identified. The corresponding quantum electronic parameters such as effective cyclotron mass and Dingle temperature were obtained using Lifshitz-Kosevich formula. From the field dependent Hall resistivity at 2 K, carrier concentrations n e (n h ) = 6.7691 (6.4352) × 1025 m-3 and mobilities µ e (µ h ) = 5.6676 (7.6947) m2 V-1 s-1 for electrons (e) and holes (h) were extracted using semiclassical two-band model fitting. We observed large anisotropic magnetoresistance about 84%, 75%, and 12% at 0.75 T and 6 K for three different orientations γ, θ and ϕ, respectively, similar to that in several topological semimetallic systems. Magnetic properties of NbAs2 are similar to the case of graphite, without any phase transition in the temperature range from 5 K to 300 K.

Crystal growth and transport properties of Weyl semimetal TaAs.

We report the single crystal growth and transport properties of a Weyl semimetal TaAs. Unsaturated large magnetoresistance of about 22 100% at 2 K and 9 T is observed. From the Hall measurement, carrier concentrations n = 4.608 × 1024 m-3 and p = 3.099 × 1024 m-3, and mobilities µ p = 2.502 m2 V-1 s-1 and µ n = 16.785 m2 V-1 s-1 at 2 K are extracted. The de Haas-van Alphen oscillations at 2 K and 9 T suggest the presence of a Fermi surface, and the quantum electronic parameters such as effective cyclotron mass and Dingle temperature were obtained using Lifshitz-Kosevich fitting. Temperature dependent resistivity measurements at different static magnetic fields suggest the formation of an insulating gap in the Weyl semimetal TaAs. An angle-resolved photoemission spectroscopy study reveals Fermi arc surface states with different shaped features such as a long elliptical contour around each [Formula: see text] point, a bowtie-shaped contour around each [Formula: see text] point, and a crescent-shaped feature near the midpoint of each [Formula: see text] line.

Crystal growth of Dirac semimetal ZrSiS with high magnetoresistance and mobility.

High quality single crystal ZrSiS as a theoretically predicted Dirac semimetal has been grown successfully using a vapor phase transport method. The single crystals of tetragonal structure are easy to cleave into perfect square-shaped pieces due to the van der Waals bonding between the sulfur atoms of the quintuple layers. Physical property measurement results including resistivity, Hall coefficient (RH), and specific heat are reported. The transport and thermodynamic properties suggest a Fermi liquid behavior with two Fermi pockets at low temperatures. At T = 3 K and magnetic field of Hǁc up to 9 Tesla, large magneto-resistance up to 8500% and 7200% for Iǁ(100) and Iǁ(110) were found. Shubnikov de Haas (SdH) oscillations were identified from the resistivity data, revealing the existence of two Fermi pockets at the Fermi level via the fast Fourier transform (FFT) analysis. The Hall coefficient (RH) showed hole-dominated carriers with a high mobility of 3.05 × 104 cm2 V-1 s-1 at 3 K. ZrSiS has been confirmed to be a Dirac semimetal by the Dirac cone mapping near the X-point via angle resolved photoemission spectroscopy (ARPES) with a Dirac nodal line near the Fermi level identified using scanning tunneling spectroscopy (STS).

Synthesis, growth, structural and optical studies of a novel organic Piperazine (bis) p-toluenesulfonate single crystal.

A novel organic single crystal of Piperazinium (bis) p-toluenesulfonate (PPTS) was grown by a slow evaporation solution growth technique. The structure of the grown crystal was determined using single crystal X-ray diffraction analysis. The PPTS crystal belongs to the triclinic crystal system with space group of P1¯. The presence of functional groups was confirmed by FTIR spectral analysis. The optical transmittance range and cut-off wavelength were identified by UV-vis-NIR spectral studies. The luminescent properties of PPTS crystal were investigated. The thermal behavior of PPTS crystal was studied by TG-DT analyses.

2-Amino-6-methyl-pyridinium 4-methyl-benzene-sulfonate.

In the asymmetric unit of the title salt, C6H9N2 (+)·C7H7O3S(-), there are two independent 2-amino-6-methyl-pyridinium cations and two independent 4-methyl-benzene-sulfonate anions. Both cations are protonated at their pyridine N atoms and their geometries reveal amine-imine tautomerism. In the 4-methyl-benzene-sulfonate anions, the carboxyl-ate groups are twisted out of the benzene ring planes by 88.4 (1) and 86.2 (2)°. In the crystal, the sulfonate O atoms of an anion inter-act with the protonated N atoms and the 2-amino groups of a cation via a pair of N-H⋯O hydrogen bonds, forming an R 2 (2)(8) ring motif. These motifs are connected via N-H⋯O hydrogen bonds, forming chains running along the a-axis direction. Within the chains there are weak C-H⋯O hydrogen bonds present. In addition, aromatic π-π stacking inter-actions [centroid-centroid distances = 3.771 (2), 3.599 (2), 3.599 (2) and 3.497 (2) Å] involving neighbouring chains are also observed.

2-Amino-6-methyl-pyridinium 2,2,2-tri-chloro-acetate.

In the asymmetric unit of the title mol-ecular salt, C6H9N2 (+)·C2Cl3O2 (-), there are two independent 2-amino-6-methyl-pyridinium cations and two independent tri-chloro-acetate anions. The pyridine N atom of the 2-amino-6-methyl-pyridine mol-ecule is protonated and the geometries of these cations reveal amine-imine tautomerism. Both protonated 2-amino-6-methyl-pyridinium cations are essentially planar [maximum deviations = 0.026 (2) and 0.012 (2) Å]. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl-ate O atoms of the anion via a pair of N-H⋯O hydrogen bonds, forming an R 2 (2)(8) ring motif. These motifs are connected via N-H⋯O and C-H⋯O hydrogen bonds to form slabs parallel to (101).

2-Carboxyl-atopyridinium-4-nitro-phenol (1/1).

In the title 1:1 adduct, C6H5NO3·C6H5NO2, both mol-ecules are almost planar (r.m.s. deviations for the non-H atoms = 0.027 and 0.023 Šfor 4-nitro-phenol and 2-carboxyl-atopyridinium, respectively). The pyridine mol-ecule crystallizes as a zwitterion (nominal proton transfer from the carb-oxy-lic acid group to the N atom in the ring). In the crystal, inversion dimers of the zwitterions linked by pairs of N-H⋯O hydrogen bonds generate R 2 (2)(10) loops; two 4-nitro-phenol mol-ecules link to the dimer by O-H⋯O hydrogen bonds, generating a four-molecule aggregate. These are linked by C-H⋯O inter-actions, forming a three-dimensional network.

1-Hy-droxy-isoquinolin-2-ium hydrogen succinate.

In the title salt, C9H8NO(+)·C4H5O4 (-), the isoquinolinium ring system is approximately planar [r.m.s deviation = 0.011 (2) Å]. In the crystal, adjacent cations and anions are linked by O-H⋯O and N-H⋯O hydrogen bonds, forming columns along the b axis. The columns are connected by weak C-H⋯O inter-actions into a three-dimensional network.

Studies on growth, structural, dielectric, laser damage threshold, linear and nonlinear optical properties of methylene blue admixtured l-arginine phosphate single crystal.

L-Arginine phosphate (LAP) and methylene blue dye admixtured L-arginine phosphate single crystals were grown by slow cooling technique and their cell parameters, crystalline perfection, dopant inclusion were confirmed by single crystal, powder X-ray diffraction and high resolution X-ray diffraction analyses respectively. The modes of vibrations of different functional groups present in pure and dye admixtured LAP crystals have been identified by FTIR spectral analysis. The UV-Vis-NIR spectral study was performed on the grown crystals and found that the crystals are transparent in the entire visible-NIR region. The dielectric measurement was carried out on the grown crystals as a function of frequency at room temperature. The microhardness hardness study on (100) plane of grown crystals reveals the mechanical behavior of the crystals. The laser damage threshold value significantly enhanced for dye admixtured crystal in comparison with pure LAP crystal. The relative SHG efficiency of methylane blue admixtured LAP crystal was found to be 1.3 times higher than that of pure LAP crystal.

Studies on synthesis, growth, structural, thermal, linear and nonlinear optical properties of organic picolinium maleate single crystals.

Picolinium maleate (PM), an organic material has been synthesised and single crystals were grown by slow evaporation technique. The structure of the grown crystal was elucidated by using single crystal X-ray diffraction analysis. PM crystal belongs to the monoclinic crystallographic system with space group P2(1)/c. The crystalline perfection of the grown crystals was analyzed by high-resolution X-ray diffraction rocking curve measurements. The presence of functional groups in PM was identified by FTIR and FT-NMR spectral analyses. Thermal behaviour and stability of picolinium maleate were studied by TGA/DTA analyses. UV-Vis spectral studies reveal that PM crystals are transparent in the wavelength region 327-1100 nm. The laser damage threshold value of PM crystal was found to be 4.3 GW/cm(2) using Nd:YAG laser. The Kurtz and Perry powder second harmonic generation technique confirms the nonlinear optical property of the grown crystal.

Dimethyl-ammonium 4-hy-droxy-benzoate.

In the crystal structure of the title compound, C(2)H(8)N(+)·C(7)H(5)O(3) (-), the anions and cations are linked by O-H⋯O and N-H⋯O hydrogen bonds into layers parallel to the ac plane.

Growth, structural, thermal, linear and nonlinear optical and laser damage threshold studies of picolinium tartrate monohydrate single crystals.

Picolinium tartrate monohydrate (PTM), a novel organic nonlinear optical material was synthesized and bulk crystals were grown from aqueous solution by slow cooling technique. The cell parameters of the grown crystal were found by single and powder X-ray diffraction analyses. The crystalline perfection of the grown crystals has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. The presence of functional groups in the grown crystal was identified by FTIR and FT-Raman spectral analyses. UV-Vis spectral studies reveal PTM crystals are transparent in the wavelength region of 295-1100 nm. The thermal characteristics of PTM were analyzed by TGA/DTA studies. The dielectric and mechanical behaviours of PTM crystals were investigated. Dislocation density was estimated to be 2.89 × 10(3) cm(-2) on the flat-surface of PTM crystals from the etching studies. The laser induced surface damage threshold for the grown crystal was measured using Nd:YAG laser. Its second harmonic generation relative efficiency was measured by Kurtz and Perry powder technique and was observed to be comparable with KDP crystal.

Synthesis, structural, optical and thermal studies of an organic nonlinear optical 4-aminopyridinium maleate single crystal.

Synthesis and growth of a novel organic nonlinear optical (NLO) crystal of 4-aminopyridinium maleate (4APM) in larger size by the slow evaporation solution growth technique are reported. Single crystal and powder X-ray diffraction analyses reveal that 4APM crystallizes in monoclinic system with space group P2(1) with cell parameters a=8.140(4)Å, b=5.457(5)Å, c=10.926(10)Å and volume=481.4(7)Å(3). The grown crystal has been characterized by Fourier transform infrared and UV-visible spectral analyses. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) have been carried out to study its thermal properties. Dielectric measurements have been carried out to study the distribution of charges within the crystal. The mechanical strength of the crystal has been studied by using Vickers' microhardness test. The etching studies have been carried out on the grown crystal. The Kurtz and Perry powder SHG technique confirms the NLO property of the grown crystal and the SHG efficiency of 4APM was found to be 4.8 times greater than that of KDP crystal.

2-Carb-oxy-pyridinium maleate.

In the title mol-ecular salt, C(6)H(6)NO(2) (+) (.)C(4)H(3)O(4) (-), the 2-carb-oxy-pyridinium cation is essentially planar with a maximum deviation of 0.003 (3) Å. In the crystal, adjacent cations and anions are linked by an extensive system of weak N-H⋯O, O-H⋯O and C-H⋯O inter-actions, forming a layer parallel to the ab plane.