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

Possible charge inhomogeneities in the CuO2 planes of YBa2Cu3O6+x (x=0.25, 0.45, 0.65, 0.94) from pulsed neutron diffraction

The atomic pair distribution functions (PDF) of four powder samples of YBa2Cu3O6+x (x=0.25, 0.45, 0.65, 0.94) at 15 K have been measured by means of pulsed neutron diffraction. The PDF is modelled using a full-profile fitting approach to yield structural parameters. In contrast to earlier XAFS work we find no evidence of a split apical oxygen site. However, a slightly improved fit over the average crystallographic model results when the planar Cu(2) site is split along the z-direction. This is interpreted in terms of charge inhomogeneities in the CuO2 planes.Comment: 8 pages, 3 figure

Charge Dynamics in Cuprate Superconductors

In this lecture we present some interesting issues that arise when the dynamics of the charge carriers in the CuO$_2$ planes of the high temperature superconductors is considered. Based on the qualitative picture of doping, set by experiments and some previous calculations, we consider the strength of various inter and intra-cell charge transfer susceptibilities, the question of Coulomb screening and charge collective modes. The starting point is the usual p-d model extended by the long range Coulomb (LRC) interaction. Within this model it is possible to examine the case in which the LRC forces frustrate the electronic phase separation, the instability which is present in the model without an LRC interaction. While the static dielectric function in such systems is negative down to arbitrarily small wavevectors, the system is not unstable. We consider the dominant electronic charge susceptibilities and possible consequences for the lattice properties.Comment: 14 pages, 15 figures, latex, to be published in "From Quantum Mechanics to Technology", Lecture Notes in Physics, Springe

High-Accuracy X-Ray Diffraction Analysis of Phase Evolution Sequence During Devitrification of Cu50Zr50 Metallic Glass

Real-time high-energy X-ray diffraction (HEXRD) was used to investigate the crystallization kinetics and phase selection sequence for constant-heating-rate devitrification of fully amorphous Cu50Zr50, using heating rates from 10 K/min to 60 K/min (10 °C/min to 60 °C/min). In situ HEXRD patterns were obtained by the constant-rate heating of melt-spun ribbons under synchrotron radiation. High-accuracy phase identification and quantitative assessment of phase fraction evolution though the duration of the observed transformations were performed using a Rietveld refinement method. Results for 10 K/min (10 °C/min) heating show the apparent simultaneous formation of three phases, orthorhombic Cu10Zr7, tetragonal CuZr2 (C11b), and cubic CuZr (B2), at 706 K (433 °C), followed immediately by the dissolution of the CuZr (B2) phase upon continued heating to 789 K (516 °C). Continued heating results in reprecipitation of the CuZr (B2) phase at 1002 K (729 °C), with the material transforming completely to CuZr (B2) by 1045 K (772 °C). The Cu5Zr8 phase, previously reported to be a devitrification product in C50Zr50, was not observed in the present study