Magnetic Structure Of R 2 Coga 8 (r = Gd, Tb, And Dy): Structural Tuning Of Magnetic Properties In Layered Ga-based Intermetallic Compounds

In this work we have determined the magnetic structure of R2CoGa8 (R= Gd, Tb, and Dy) intermetallic compounds using x-ray resonant magnetic scattering in order to study the evolution of the anisotropic magnetic properties along the series for R= Gd-Tm. The three compounds have a commensurate antiferromagnetic spin structure with a magnetic propagation vector τâ- = (12,12,12) and a Néel temperature of approximately 20, 28.5, and 15.2 K for R= Gd, Tb, and Dy, respectively. The critical exponent β obtained from the temperature dependence of the magnetic peaks suggest a three-dimensional universality class for the three compounds. Comparing the simulated and integrated intensities we conclude that the magnetic moment direction is in the ab plane for the Gd2CoGa8 compound and parallel to the c axis for the Tb2CoGa8 and Dy2CoGa8 compounds. The evolution of the magnetic properties of the R2CoGa8 series for R= Gd-Tm is discussed taking into account the indirect Ruderman-Kittel-Kasuya-Yoshida interaction and crystalline-electric field effects. The comparison between the reported magnetic properties of the Ga-based compounds with those for the In-based isostructural family reveals differences in their exchange couplings that contribute to the understanding of the role of the f-electron magnetism in these classes of materials. © 2014 American Physical Society.8911Thompson, J., Fisk, Z., (2012) J. Phys. Soc. Jpn., 81, p. 011002. , JUPSAU 0031-9015 10.1143/JPSJ.81.011002Movshovich, R., Jaime, M., Thompson, J.D., Petrovic, C., Fisk, Z., Pagliuso, P.G., Sarrao, J.L., (2001) Phys. Rev. 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PRBMDO 0163-1829 10.1103/PhysRevB.64.020401Granado, E., Pagliuso, P.G., Giles, C., Lora-Serrano, R., Yokaichiya, F., Sarrao, J.L., (2004) Phys. Rev. B, 69, p. 144411. , PRBMDO 1098-0121 10.1103/PhysRevB.69.144411Adriano, C., Giles, C., Coelho, L., Faria, G., Pagliuso, P., (2009) Physica B, 404, p. 3289. , PHYBE3 0921-4526 10.1016/j.physb.2009.07.127Adriano, C., Aliouane, N., Mardegan, J.R.L., Coelho, L.N., Escovi, R.V., Pagliuso, P.G., Giles, C., (unpublished)Johnson, R.D., Frawley, T., Manuel, P., Khalyavin, D.D., Adriano, C., Giles, C., Pagliuso, P.G., Hatton, P.D., (2010) Phys. Rev. B, 82, p. 104407. , PRBMDO 1098-0121 10.1103/PhysRevB.82.104407Fisk, Z., Remeika, J., Gschneider, K.A., Eyring, L., (1989) Handbook on the Physics and Chemistry of Rare Earths, p. 53. , edited by, Vol. 12 (Elsevier, AmsterdamJoshi, D.A., Nagalakshmi, R., Dhar, S.K., Thamizhavel, A., (2008) Phys. Rev. B, 77, p. 174420. , PRBMDO 1098-0121 10.1103/PhysRevB.77.174420Giles, C., Yokaichiya, F., Kycia, S., Sampaio, L., Ardiles-Saravia, D., Franco, M., Neuenschwander, R., (2003) J. Synchrotron Rad., 10, p. 430. , JSYRES 0909-0495 10.1107/S0909049503020958Vaillant, F., (1977) Acta Cryst. A, 33, p. 967. , ACACBN 0567-7394 10.1107/S0567739477002307Hill, J., McMorrow, D., (1996) Acta Cryst. A, 52, p. 236. , ACACEQ 0108-7673 10.1107/S0108767395012670Joly, Y., (2001) Phys. Rev. B, 63, p. 125120. , PRBMDO 1098-0121 10.1103/PhysRevB.63.125120Gibbs, D., Grubel, G., Harshman, D.R., Isaacs, E.D., McWhan, D.B., Mills, D., Vettier, C., (1991) Phys. Rev. B, 43, p. 5663. , PRBMDO 0163-1829 10.1103/PhysRevB.43.5663Collins, M.F., (1989) Magnetic Critical Scattering, , (Oxford University Press, Oxford)Wills, A., (2000) Physica B, p. 680. , PHYBE3 0921-4526 10.1016/S0921-4526(99)01722-6Detlefs, C., Islam, A.H.M.Z., Goldman, A.I., Stassis, C., Canfield, P.C., Hill, J.P., Gibbs, D., (1997) Phys. Rev. B, 55, pp. R680. , PRBMDO 0163-1829 10.1103/PhysRevB.55.R680Nandi, S., Su, Y., Xiao, Y., Price, S., Wang, X.F., Chen, X.H., Herrero-Martín, J., Brückel, Th., (2011) Phys. Rev. B, 84, p. 054419. , PRBMDO 1098-0121 10.1103/PhysRevB.84.054419Blundell, S., (2001) Magnetism in Condensed Matter, , Oxford Master Series in Condensed Matter Physics (Oxford University Press, Oxford)The density of states at the Fermi level for Gd 2 IrIn 8 was estimated using the electronic contribution to the heat capacity γ measured for the isomorphous reference compound La 2 IrIn 8Kovalev, O.V., Stokes, H.T., Hatch, D.M., (1993) Representations of the Crystallographic Space Groups, , 2nd ed., edited by (Gordon and Breach Science Publishers, Yverdon, Switzerland

Magnetic properties of GdT2T_2Zn20_{20} (T = Fe, Co) investigated by X-ray diffraction and spectroscopy

We investigate the magnetic and electronic properties of the Gd$T_2$Zn$_{20}$ ($T$ = Fe and Co) compounds using X-ray resonant magnetic scattering (XRMS), X-ray absorption near-edge structure (XANES) and X-ray magnetic circular dichroism (XMCD) techniques. The XRMS measurements reveal that the GdCo$_2$Zn$_{20}$ compound has a commensurate antiferromagnetic spin structure with a magnetic propagation vector $\vec{\tau}$ = $(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ below the N\'eel temperature ($T_N \sim$ 5.7 K). Only the Gd ions carry a magnetic moment forming an antiferromagnetic structure with magnetic representation $\Gamma_6$. For the ferromagnetic GdFe$_2$Zn$_{20}$ compound, an extensive investigation was performed at low temperature and under magnetic field using XANES and XMCD techniques. A strong XMCD signal of about 12.5 $\%$ and 9.7 $\%$ is observed below the Curie temperature ($T_C \sim$ 85 K) at the Gd-$L_2$ and $L_3$ edges, respectively. In addition, a small magnetic signal of about 0.06 $\%$ of the jump is recorded at the Zn $K$-edge suggesting that the Zn 4$p$ states are spin polarized by the Gd 5$d$ extended orbitals

Magnetic Properties Of Gdt2zn20 (t=fe, Co) Investigated By X-ray Diffraction And Spectroscopy

We investigate the magnetic and electronic properties of the GdT2Zn20 (T=Fe and Co) compounds using x-ray resonant magnetic scattering (XRMS), x-ray absorption near-edge structure (XANES), and x-ray magnetic circular dichroism (XMCD). The XRMS measurements reveal that GdCo2Zn20 has a commensurate antiferromagnetic spin structure with a magnetic propagation vector τ - =(12,12,12) below the Néel temperature (TN∼5.7 K). Only the Gd ions carry a magnetic moment forming an antiferromagnetic structure with magnetic representation Γ6. For the ferromagnetic GdFe2Zn20 compound, an extensive investigation was performed at low temperature and under magnetic field using XANES and XMCD. A strong XMCD signal of about 12.5% and 9.7% is observed below the Curie temperature (TC∼85K) at the Gd L2 and L3 edges, respectively. In addition, a small magnetic signal of about 0.06% of the jump is recorded at the Zn K edge, suggesting that the Zn 4p states are spin polarized by the Gd 5d extended orbitals. © 2016 American Physical Society.93

A counterion study of a series of [Cu(P^P)(N^N)][A] compounds with bis(phosphane) and 6-methyl and 6,6'-dimethyl-substituted 2,2'-bipyridine ligands for light-emitting electrochemical cells

The syntheses and characterisations of a series of heteroleptic copper(i) compounds [Cu(POP)(Mebpy)][A], [Cu(POP)(Me(2)bpy)][A], [Cu(xantphos)(Mebpy)][A] and [Cu(xantphos)(Me(2)bpy)][A] in which [A](-) is [BF4](-), [PF6](-), [BPh4](-) and [BAr4F](-) (Mebpy = 6-methyl-2,2 '-bipyridine, Me(2)bpy = 6,6 '-dimethyl-2,2 '-bipyridine, POP = oxydi(2,1-phenylene)bis(diphenylphosphane), xantphos = (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane), [BAr4F](-) = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) are reported. Nine of the compounds have been characterised by single crystal X-ray crystallography, and the consequences of the different anions on the packing interactions in the solid state are discussed. The effects of the counterion on the photophysical properties of [Cu(POP)(NN)][A] and [Cu(xantphos)(NN)][A] (NN = Mebpy and Me(2)bpy) have been investigated. In the solid-state emission spectra, the highest energy emission maxima are for [Cu(xantphos)(Mebpy)][BPh4] and [Cu(xantphos)(Me(2)bpy)][BPh4] (lambda emmax = 520 nm) whereas the lowest energy lambda emmax values occur for [Cu(POP)(Mebpy)][PF6] and [Cu(POP)(Mebpy)][BPh4] (565 nm and 563 nm, respectively). Photoluminescence quantum yields (PLQYs) are noticeably affected by the counterion; in the [Cu(xantphos)(Me(2)bpy)][A] series, solid-state PLQY values decrease from 62% for [PF6](-), to 44%, 35% and 27% for [BF4](-), [BPh4](-) and [BAr4F](-), respectively. This latter series of compounds was used as active electroluminescent materials on light-emitting electrochemical cells (LECs). The luminophores were mixed with ionic liquids (ILs) [EMIM][A] ([EMIM](+) = [1-ethyl-3-methylimidazolium](+)) containing the same or different counterions than the copper(i) complex. LECs containing [Cu(xantphos)(Me(2)bpy)][BPh4] and [Cu(xantphos)(Me(2)bpy)][BAr4F] failed to turn on under the LEC operating conditions, whereas those with the smaller [PF6](-) or [BF4](-) counterions had rapid turn-on times and exhibited maximum luminances of 173 and 137 cd m(-2) and current efficiencies of 3.5 and 2.6 cd A(-1), respectively, when the IL contained the same counterion as the luminophore. Mixing the counterions ([PF6](-) and [BF4](-)) of the active complex and the IL led to a reduction in all the figures of merit of the LECs

Fabrication and optical properties of strain-free self-assembled mesoscopic GaAs structures

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESWe use a combined process of Ga-assisted deoxidation and local droplet etching to fabricate unstrained mesoscopic GaAs/AlGaAs structures exhibiting a high shape anisotropy with a length up to 1.2 mu m and a width of 150 nm. We demonstrate good controllability over size and morphology of the mesoscopic structures by tuning the growth parameters. Our growth method yields structures, which are coupled to a surrounding quantum well and present unique optical emission features. Microscopic and optical analysis of single structures allows us to demonstrate that single structure emission originates from two different confinement regions, which are spectrally separated and show sharp excitonic lines. Photoluminescence is detected up to room temperature making the structures the ideal candidates for strain-free light emitting/detecting devices.12114FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES2012/11382-92014/17141-92015/08344-62016/14001-7475343/2013-1482729/2013-9305769/2015-4Sem informaçãoThe financial support through SisNano (MCTI Brazil), FAPESP (Processo 2012/11382-9, 2014/17141-9, 2015/08344-6 and 2016/14001-7), and CNPq (Processo 482729/2013-9, 305769/2015-4, 475343/2013-1) is acknowledged. SFCS thanks CAPES for the scholarship

Chlamydia pneumoniae and Mycoplasma pneumoniae in children with cystic fibrosis: impact on bacterial respiratory microbiota diversity.

The contribution of intracellular and fastidious bacteria in Cystic fibrosis (CF) pulmonary exacerbations, and progressive lung function decline remains unknown. This project aimed to explore their impact on bacterial microbiota diversity over time in CF children. Sixty-one children enrolled in the MUCOVIB multicentre prospective cohort provided 746 samples, mostly nasopharyngeal swabs, throat swabs and sputa which were analysed using culture, specific real-time qPCRs and 16S rRNA amplicon metagenomics. Chlamydia pneumoniae (n = 3) and Mycoplasma pneumoniae (n = 1) were prospectively documented in 6.6% of CF children. Microbiota alpha-diversity in children with a documented C. pneumoniae was highly variable, similarly to children infected with Staphylococcus aureus or Pseudomonas aeruginosa. The transition from routine follow-up visits to pulmonary exacerbation (n = 17) yielded variable changes in diversity indexes with some extreme loss of diversity. The high rate of C. pneumoniae detection supports the need for regular screenings in CF patients. A minor impact of C. pneumoniae on the microbial community structure was documented. Although detected in a single patient, M. pneumoniae should also be considered as a possible aetiology of lung infection in CF subjects

Silver doping of silica-hafnia waveguides containing Tb3+/Yb3+ rare earths for downconversion in PV solar cells

The aim of this paper is to study the possibility to obtain an efficient downconverting waveguide which combines the quantum cutting properties of Tb3+/Yb3+ codoped materials with the optical sensitizing effects provided by silver doping. The preparation of 70SiO(2)-30HfO(2) glass and glass-ceramic waveguides by sol-gel route, followed by Ag doping by immersion in molten salt bath is reported. The films were subsequently annealed in air to induce the migration and/or aggregation of the metal ions. Results of compositional and optical characterization are given, providing evidence for the successful introduction of Ag in the films, while the photoluminescence emission is strongly dependent on the annealing conditions. These films could find potential applications as downshifting layers to increase the efficiency of PV solar cells. (C) 2016 Elsevier B.V. All rights reserved

Action of Coriandrum sativum L. Essential Oil upon Oral Candida albicans Biofilm Formation

The efficacy of extracts and essential oils from Allium tuberosum, Coriandrum sativum, Cymbopogon martini, Cymbopogon winterianus, and Santolina chamaecyparissus was evaluated against Candida spp. isolates from the oral cavity of patients with periodontal disease. The most active oil was fractionated and tested against C. albicans biofilm formation. The oils were obtained by water-distillation and the extracts were prepared with macerated dried plant material. The Minimal Inhibitory Concentration—MIC was determined by the microdilution method. Chemical characterization of oil constituents was performed using Gas Chromatography and Mass Spectrometry (GC-MS). C. sativum activity oil upon cell and biofilm morphology was evaluated by Scanning Electron Microscopy (SEM). The best activities against planktonic Candida spp. were observed for the essential oil and the grouped F8–10 fractions from C. sativum. The crude oil also affected the biofilm formation in C. albicans causing a decrease in the biofilm growth. Chemical analysis of the F8–10 fractions detected as major active compounds, 2-hexen-1-ol, 3-hexen-1-ol and cyclodecane. Standards of these compounds tested grouped provided a stronger activity than the oil suggesting a synergistic action from the major oil constituents. The activity of C. sativum oil demonstrates its potential for a new natural antifungal formulation