Magnetic And Superconducting Properties Of Ru Sr2 Gd1.5 Ce0.5 Cu2 O10-δ Samples: Dependence On The Oxygen Content And Aging Effects

The magnetic and superconducting properties of Ru Sr2 Gd1.5 Ce0.5 Cu2 O10-δ polycrystalline samples with different oxygen-doping levels are presented. A strong suppression of the superconducting temperature (Tc), as well as a reduction in the superconducting fraction, occurs as the oxygen content is reduced by annealing the samples in oxygen-deprived atmospheres. Drastic changes in the electrical resistivity are observed above Tc, possibly associated with oxygen removal, mainly from grain boundaries. However, the magnetic ordering is relatively less affected by the changes in oxygen content of the samples. The spin-glass transition is enhanced and shifted to higher temperatures with the reduction in oxygen content. This could be correlated with an increase in the spin disorder and frustration for the oxygen-depleted samples. Also, the same oxygen-vacancy-induced disorder could explain the reduction in the fraction of the sample showing antiferromagnetic order. We also report significant changes in the measured properties of the samples as a function of time. © 2005 The American Physical Society.7113Felner, I., Asaf, U., Levi, Y., Millo, O., (1997) Phys. Rev. B, 55, p. 3374. , PRBMDO 0163-1829 10.1103/PhysRevB.55.R3374Bernhard, C., Tallon, J.L., Niedermayer, Ch., Blasius, Th., Golnik, A., Brücher, E., Kremer, R.K., Ansaldo, E.J., (1999) Phys. Rev. B, 59, p. 14099. , PRBMDO. 0163-1829. 10.1103/PhysRevB.59.14099Awana, V.P.S., Karppinen, M., Yamauchi, H., (2003) Studies of High Tc Superconductors, 46, p. 77. , edited by A. V. Narlikar (Nova Science Publishers, New YorkMatvejeff, M., Awana, V.P.S., Jang, L.-Y., Liu, R.S., Yamauchi, H., Karppinen, M., (2003) Physica C, 392-396, p. 87. , PHYCE6 0921-4534Cardoso, C.A., Araujo-Moreira, F.M., Awana, V.P.S., Kishan, H., Takayama-Muromachi, E., De Lima, O.F., (2004) Physica C, 405, p. 212. , PHYCE6 0921-4534Cardoso, C.A., Araujo-Moreira, F.M., Awana, V.P.S., Takayama-Muromachi, E., De Lima, O.F., Yamauchi, H., Karppinen, M., (2003) Phys. Rev. B, 67, p. 020407. , PRBMDO 0163-1829 10.1103/PhysRevB.67.020407Shi, L., Li, G., Fan, X.J., Feng, S.J., Li, X.-G., (2003) Physica C, 399, p. 69. , PHYCE6 0921-4534Felner, I., Asaf, U., Ritter, F., Klamut, P.W., Dabrowski, B., (2001) Physica C, 364-365, p. 368. , PHYCE6 0921-4534Felner, I., Asaf, U., Galstyan, E., (2002) Phys. Rev. B, 66, p. 024503. , PRBMDO 0163-1829 10.1103/PhysRevB.66.024503Felner, I., Asaf, U., Levi, Y., Millo, O., (2000) Physica C, 334, p. 141. , PHYCE6 0921-4534 10.1016/S0921-4534(00)00250-1Awana, V.P.S., Ansari, M.A., Gupta, A., Saxena, R.B., Kishan, H., Buddhikot, D., Malik, S.K., (2004) Phys. Rev. B, 70, p. 104520. , PRBMDO 0163-1829 10.1103/PhysRevB.70.104520Yoshizawa, H., Mitsuda, S., Aruga, H., Ito, A., (1987) Phys. Rev. Lett., 59, p. 2364. , PRLTAO 0031-9007 10.1103/PhysRevLett.59.2364Binder, K., Young, A.P., (1986) Rev. Mod. Phys., 58, p. 801. , RMPHAT 0034-6861 10.1103/RevModPhys.58.801Mydosh, J.A., (1993) Spin Glasses An Experimental Introduction, , Taylor & Francis, LondonFelner, I., Galstyan, E., Herber, R.H., Nowik, I., (2004) Phys. Rev. B, 70, p. 094504. , PRBMDO 0163-1829 10.1103/PhysRevB.70.094504Shengelaya, A., Khasanov, R., Eschenko, D.G., Felner, I., Asaf, U., Savić, I.M., Keller, H., Müller, K.A., (2004) Phys. Rev. B, 69, p. 024517. , PRBMDO. 0163-1829. 10.1103/PhysRevB.69.024517Xue, Y.Y., Cao, D.H., Lorenz, B., Chu, C.W., (2002) Phys. Rev. B, 65, p. 020511. , PRBMDO 0163-1829 10.1103/PhysRevB.65.02051

Structural And Magnetic Study Of Labacocu O5+δ

The structure and magnetic properties of the compound LaBaCuCo O5+δ have been studied for the non-stoichiometric oxygen concentration δ≈0.6. The structure is pseudo-cubic with a tripled perovskite unit cell. The crystal structure was determined by a combined Rietveld fit to neutron and synchrotron x-ray powder diffraction data in the orthorhombic Pmmm space group, with cell parameters a=3.9223 (3) Å, b=3.9360 (3) Å, c=11.7073 (8) Å, and V=180.74 (2) Å3 (room temperature). Antiferromagnetic ordering of Cu and Co magnetic moments is observed below 205 (4) K. The magnetic structure with cell aM =2a, bM =2b, and cM =2c, could be described with the Shubnikov space group Fmm m′. The magnetic moments of both equivalent Cu/Co sites were determined at 50 and 170 K to be 0.83 (3) μB and 0.58 (3) μB, respectively, consistent with one unpaired electron per atom. The fit of the intensities to a simple mean field magnetic model appeared to be insufficient to account for the variation of moments at temperatures close to TN while a three dimensional Heisenberg model could improve the fit. Susceptibility measurements between 4 and 350 K also show irreversibility below 150 K. The local environments of Cu and Co were studied by extended x-ray absorption fine structure spectroscopy at both absorption edges. Cu atoms adopt an elongated octahedral or square-based pyramidal oxygen environment which suggests mainly the presence of Cu(II) in the structure. Co adopts different local environments, depending on the electronic and spin states. © 2005 The American Physical Society.7114Er-Rakho, L., Michel, C., Lacorre, P., Raveau, B., (1988) J. Solid State Chem., 73, p. 531. , JSSCBI 0022-4596 10.1016/0022-4596(88)90141-7Meyer, C., Hartmann-Boutron, F., Gros, Y., Strobel, P., (1990) Solid State Commun., 76, p. 163. , SSCOA4 0038-1098 10.1016/0038-1098(90)90535-JAtanassova, Y.K., Popov, V.N., Bogachev, G.G., Iliev, M.N., Mitros, C., Psycharis, V., Pissas, M., (1993) Phys. Rev. B, 47, p. 15201. , PRBMDO 0163-1829 10.1103/PhysRevB.47.15201Mombrú, A.W., Christides, C., Lappas, A., Prassides, K., Pissas, M., Mitros, C., Niarchos, D., (1994) Inorg. Chem., 33, p. 1255. , INOCAJ. 0020-1669Caignaert, V., Mirebeau, I., Bouree, F., Nguyen, N., Ducouret, A., Greneche, J.M., Raveau, B., (1995) J. Solid State Chem., 114, p. 24. , JSSCBI 0022-4596 10.1006/jssc.1995.1004Mombrú, A.W., Prassides, K., Christides, C., Erwin, R., Pissas, M., Niarchos, C., Mitros, D., (1998) J. Phys.: Condens. Matter, 10, p. 1247. , JCOMEL. 0953-8984. 10.1088/0953-8984/10/6/008Ruiz-Aragón, M., Amador, U., Morán, E., Andersen, N.H., (1994) Physica C, 235-240, p. 1609. , PHYCE6. 0921-4534Pissas, M., Mitros, C., Kallias, G., Psycharis, V., Niarchos, D., Simopoulos, A., Kostikas, A., Prassides, K., (1991) Physica C, 185, p. 553. , PHYCE6 0921-4534Pissas, M., Mitros, C., Kallias, G., Psycharis, V., Simopoulos, A., Kostikas, A., Niarchos, D., (1992) Physica C, 192, p. 35. , PHYCE6 0921-4534 10.1016/0921-4534(92)90740-4Er-Rakho, L., Michel, C., Studer, F., Raveau, B., (1977) J. Phys. Chem. Solids, 48, p. 377. , JPCSAW 0022-3697Pardo, H., Ortiz, W.A., Araújo-Moreira, F.M., Suescun, L., Toby, B., Quagliata, E., Negreira, C.A., Mombrú, A.W., (1999) Physica C, 313, p. 105. , PHYCE6. 0921-4534. 10.1016/S0921-4534(98)00668-6Mombrú, A.W., Pardo, H., Suescun, L., Toby, B.H., Ortiz, W.A., Negreira, C.A., Araújo-Moreira, F.M., (2001) Physica C, 356, p. 149. , PHYCE6. 0921-4534Mombrú, A.W., Goeta, A.E., Pardo, H., Lisboa-Filho, P.N., Suescun, L., Mariezcurrena, R.A., Ventura, O.N., Araújo-Moreira, F.M., (2002) J. Solid State Chem., 166, p. 251. , JSSCBI. 0022-4596Guskos, N., Likodimos, V., Kuriata, J., Metz, H., Windsch, W., Wabia, M., Mitros, C., Niarchos, D., (1994) Phys. Status Solidi B, 181, p. 69. , PSSBBD 0370-1972Ruiz-Aragón, M.J., Morán, E., Amador, U., Martínez, J.L., Andersen, N.H., Ehrenberg, H., (1998) Phys. Rev. B, 58, p. 6291. , PRBMDO. 0163-1829. 10.1103/PhysRevB.58.6291Pissas, M., Kallias, G., Psycharis, V., Gamari-Seale, H., Niarchos, D., Simopoulos, A., Sonntag, R., (1997) Phys. Rev. B, 55, p. 397. , PRBMDO 0163-1829 10.1103/PhysRevB.55.397Potze, R.H., Sawatzky, G.A., Abbate, M., (1995) Phys. Rev. B, 51, p. 11501. , PRBMDO 0163-1829 10.1103/PhysRevB.51.11501Takahashi, H., Munakata, F., Yamanaka, M., (1998) Phys. Rev. B, 57, p. 15211. , PRBMDO 0163-1829 10.1103/PhysRevB.57.15211Chappel, E., Holzapfel, M., Chouteau, G., Ott, A., (2000) J. Solid State Chem., 154, p. 451. , JSSCBI 0022-4596Krimmel, A., Reehuis, M., Paraskevopoulos, M., Hemberger, J., Loidl, A., (2001) Phys. Rev. B, 64, p. 224404. , PRBMDO 0163-1829 10.1103/PhysRevB.64.224404Brinks, H.W., Fjellvåg, H., Kjekshus, A., Hauback, B.C., (1999) J. Solid State Chem., 147, p. 467. , JSSCBI. 0022-4596Pouchard, M., Villesuzanne, A., Doumerc, J.P., (2001) J. Solid State Chem., 162, p. 282. , JSSCBI 0022-4596 10.1006/jssc.2001.9294Paraskevopoulos, M., Hemberger, J., Krimmel, A., Loidl, A., (2001) Phys. Rev. B, 63, p. 224416. , PRBMDO 0163-1829 10.1103/PhysRevB.63.224416Nakatsugawa, H., Iguchi, E., (2001) J. Solid State Chem., 159, p. 215. , JSSCBI 0022-4596Hansteen, O.H., Fjellvåg, H., Hauback, B.C., (1998) J. Solid State Chem., 141, p. 411. , JSSCBI. 0022-4596Fauth, F., Suard, E., Caignaert, V., (2001) Phys. Rev. B, 65, p. 060401. , PRBMDO 0163-1829 10.1103/PhysRevB.65.060401Huang, Q.Z., Karen, V.L., Santoro, A., Kjekshus, A., Lindén, J., Pietari, T., Karen, P., (2003) J. Solid State Chem., 172, p. 73. , JSSCBI. 0022-4596Barbey, L., Nguyen, N., Caignaert, V., Hervieu, M., Raveau, B., (1992) Mater. Res. Bull., 27, p. 295. , MRBUAC 0025-5408 10.1016/0025-5408(92)90058-8Zaliznyak, I.A., Tranquada, J.M., Erwin, R., Moritomo, Y., (2001) Phys. Rev. B, 64, p. 195117. , PRBMDO 0163-1829 10.1103/PhysRevB.64.195117Wu, J., Leighton, C., (2003) Phys. Rev. B, 67, p. 174408. , PRBMDO 0163-1829 10.1103/PhysRevB.67.174408Ibarra, M.R., Mahendiran, R., Marquina, C., García-Landa, B., Blasco, J., (1998) Phys. Rev. B, 57, p. 3217. , PRBMDO. 0163-1829. 10.1103/PhysRevB.57.R3217Huang, Q., Karen, P., Karen, V.L., Kjekshus, A., Lynn, J.W., Mighell, A.D., Natali Sora, I., Santoro, A., (1994) J. Solid State Chem., 108, p. 80. , JSSCBI 0022-4596 10.1006/jssc.1994.1012http://www.ncnr.nist.gov/Larson, A.C., Von Dreele, R.B., (1987), LA-UR-86-748Toby, B.H., (2001) J. Appl. Crystallogr., 34, p. 210. , JACGAR 0021-8898 10.1107/S0021889801002242Von Dreele, R.B., (1994)Newville, M., Ravel, B., (2001)Torardi, C.C., McCarron III, E.M., Subramanian, M.A., Sleight, A.W., Cox, D.E., (1987) Mater. Res. Bull., 22, p. 1563. , MRBUAC 0025-5408Demazeau, G., Parent, C., Pouchard, M., Hagenmueller, P., (1972) Mater. Res. Bull., 7, p. 913. , MRBUAC 0025-5408David, W.I.F., Harrison, W.T.A., Ibberson, R.M., Weller, M.T., Grasmeder, J.R., Lanchester, P.C., (1987) Nature (London), 328, p. 328. , NATUAS 0028-0836Izumi, F., Asano, H., Ishigaki, T., Takayama-Muromachi, E., Matsui, Y., Uchida, Y., (1987) Jpn. J. Appl. Phys., Part 2, 26, p. 1153. , JAPLD8 0021-4922Izumi, F., Takayama-Muromachi, E., Kobayashi, M., Uchida, Y., Asano, H., Ishigaki, T., Watanabe, N., (1988) Jpn. J. Appl. Phys., Part 2, 27, p. 824. , JAPLD8 0021-4922Domenges, B., Hervieu, M., Michel, C., Maignan, A., Raveau, B., (1988) Phys. Status Solidi a, 107, p. 73. , PSSABA 0031-8965Ruiz-González, L., Boulahya, K., Parras, M., Alonso, J., González-Calbet, J.M., (2002) Chem.-Eur. J., 8 (24), p. 5694. , CEUJED. 0947-6539Shubnikov, A.V., Belov, N.V., (1964) Colored Symmetry, , Pergamon Press, Oxfor

Spatial and temporal variation of fish assemblage associated with aquatic macrophyte patches in the littoral zone of the Ayapel Swamp Complex, Colombia

ABSTRACT: Aim: The purpose of the present study was to examine spatial and temporal variation in fish assemblage structure associated with aquatic macrophytes in the littoral zone of the ASC. Methods: Specimens were caught between January 2008 and February 2009, over four limnimetric moments, using both cast net and seine net. Data on the temperature, electrical conductivity, pH and dissolved oxygen was recorded for the characterization of the water mass in the sites. Results: A total of 34,151 specimens from 44 species were collected. The most abundant species were Eigenmannia virescens, Astyanax caucanus, Astyanax fasciatus, Roeboides dayi and Cyphocharax magdalenae, which together accounted for more than 75% of the sample. Temporal and spatial comparisons showed variation in the environmental conditions and highlighted the existence of heterogeneous abiotic conditions (p0.05) regarding the fish assemblage structure. The multivariate analysis showed no significant relationship between existing environmental conditions and the fish assemblage (p=0.04). The analysis also showed the absence of a relationship between the fish assemblage and environmental variables with respect to the flood pulse and sampling sites (p>0.05). Conclusion: The uniformity of the fish communities that inhabit aquatic macrophyte patches in the littoral region of the ASC may be related to the availability of suitable habitat in structural terms, that probably supports a more abundant and varied wildlife

Local hydrological conditions influence tree diversity and composition across the Amazon basin

Tree diversity and composition in Amazonia are known to be strongly determined by the water supplied by precipitation. Nevertheless, within the same climatic regime, water availability is modulated by local topography and soil characteristics (hereafter referred to as local hydrological conditions), varying from saturated and poorly drained to well-drained and potentially dry areas. While these conditions may be expected to influence species distribution, the impacts of local hydrological conditions on tree diversity and composition remain poorly understood at the whole Amazon basin scale. Using a dataset of 443 1-ha non-flooded forest plots distributed across the basin, we investigate how local hydrological conditions influence 1) tree alpha diversity, 2) the community-weighted wood density mean (CWM-wd) – a proxy for hydraulic resistance and 3) tree species composition. We find that the effect of local hydrological conditions on tree diversity depends on climate, being more evident in wetter forests, where diversity increases towards locations with well-drained soils. CWM-wd increased towards better drained soils in Southern and Western Amazonia. Tree species composition changed along local soil hydrological gradients in Central-Eastern, Western and Southern Amazonia, and those changes were correlated with changes in the mean wood density of plots. Our results suggest that local hydrological gradients filter species, influencing the diversity and composition of Amazonian forests. Overall, this study shows that the effect of local hydrological conditions is pervasive, extending over wide Amazonian regions, and reinforces the importance of accounting for local topography and hydrology to better understand the likely response and resilience of forests to increased frequency of extreme climate events and rising temperatures