Buckling of the CuO2 Plane in Single Crystals of La-Based High-TC Cuprates Observed by NMR (original) (raw)
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NMR study on the local structure in La-based high- T c cuprates
Journal of Physics: Conference Series, 2008
To date, there has been no evidence for the macroscopic structural phase transition to the low temperature tetragonal structure (LTT) with a space group P4 2 /ncm in high-T C cuprate of rare earth-free La 2−x Sr x CuO 4 (LSCO). By investigating Cu-NMR on single crystals, we have found that spatially incoherent LTT structure emerges below 50 K in the sample with x=0.12. This incoherent structure is considered to play a key role for the slight depression of the superconductivity around x=1/8.
Planar Cu and O hole densities in high-Tc cuprates determined with NMR
Physical Review B, 2004
The electric hyperfine interaction observable in atomic spectroscopy for O and Cu ions in various configurations is used to analyze the quadrupole splitting of O and Cu nuclear magnetic resonance (NMR) in La 2-x Sr x CuO 4 and YBa 2 Cu 3 O 6+y and to determine the hole densities at both sites as a function of doping. It is found that in La 2-x Sr x CuO 4 all doped holes (x) reside in the Cu-O plane but almost exclusively at O. For YBa 2 Cu 3 O 6+y and y<0.6 doped holes are found at planar Cu as well as O. For y>0.6 further doping increases the hole content only for planar O. The phase diagram based on NMR data is presented. Further implications from the Cu A and B site in La 2-x Sr x CuO 4 and the two planar O sites in YBa 2 Cu 3 O 6+y and consequences for the phase diagram are discussed.
NMR evidence for spatial modulations in the cuprates
Journal of Superconductivity, 2000
Nuclear magnetic resonance (NMR) data on Cu, apical and planar O in La1.85Sr0.15CuO4 are presented. Spin echo double resonance shows that the large Cu magnetic shift distribution is of short-length scale. Analysis of the O data reveals static modulations of the spin susceptibility with a spin–spin correlation function near zero. The Cu shift distribution is found to be of orbital origin. The full planar oxygen spectra show a correlated modulation of the electric field gradient with the spin susceptibility. Similar results on other cuprates indicate universality of these phenomena.
Physica C: Superconductivity, 2007
Crystal structures of Co-based 1212-type layered cuprates, CoSr 2 (Y 1Àx Ca x )Cu 2 O 7+d (x = 0, 0.4; d = 0, 0.3) have been investigated by means of transmission electron microscopy (TEM). For the non-superconductive CoSr 2 YCu 2 O 7.0 parent phase (x = 0, d = 0), electron diffraction (ED) patterns revealed superlattice reflections due to an ordered arrangement of two kinds of chain of CoO 4 tetrahedra that are mirror images of each other, along the b direction. In the non-superconductive CoSr 2 (Y 0.6 Ca 0.4 )Cu 2 O 7.0 phase (x = 0.4, d = 0), the superlattice reflections were found to be streaked along the b * direction, indicating that the partially disordered arrangement is induced by aliovalent Ca II -for-Y III substitution. In the superconductive CoSr 2 (Y 0.6 Ca 0.4 )Cu 2 O 7.3 phase (x = 0.4, d = 0.3), the superlattice reflections are not seen anymore, suggesting that the distinction of the two CoO 4 chains has disappeared. Furthermore, high-resolution TEM observation revealed that the introduced excess oxygen atoms interrupt the regular shift of the chain position along the c direction.
Determination of the Local Lattice Distortions in the CuO2 Plane of La1.85Sr0.15CuO4
Physical Review Letters, 1996
The measurement of the Cu-O distances by a local and fast probe, polarized Cu K-edge extended x-ray absorption fine structure (EXAFS) in La 1.85 Sr 0.15 CuO 4 crystal shows two different conformations of the CuO 6 octahedra below 100 K assigned to two types of stripes with different lattice. This experiment supports a model of "two components" spatially separated in a superlattice of quantum stripes for the anomalous properties of cuprate superconductors. [S0031-9007(96)00119-6]
Local Structural Distortions and Phase Separation in Cuprates
Journal of Superconductivity, 2004
We report evidence from Raman measurements of local lattice distortions in the cuprates, which are induced at room temperature by varying the hydrostatic pressure and correlate with changes in the superconducting transition temperature. Anomalous nonlinear pressure dependence is observed for almost all A g phonons of the YBa 2 Cu 3 O 6.5 , YBa 2 Cu 3 O over , and YBa 2 Cu 4 O 8 superconducting single crystals, which occurs at pressures where the transition temperature shows also characteristic changes. The results are compared with a similar correlation found between transition temperature and spectral modifications in Bi 2 Sr 2 CaCu 2 O 8 by pressure and in YBa 2 Cu 3 O x and La 2-x Sr x CuO 4 by chemical doping. There are strong indications that the saturation of T c with pressure or compositional doping in these cuprates is mainly related with lattice instabilities and probably also with phase separation phenomena.
Lattice effects in the La$_{\rm 2-x}$Sr$_{\rm x}$CuO$_{\rm 4}$ compounds
2009
Systematic Raman studies on several cuprates (YBa 2 Cu 3 O x , YBa 2 Cu 4 O 8 or Bi 2 Sr 2 CaCu 2 O 8 ) have shown that at optimal doping the compounds are at the edge of lattice instability; once this level is exceeded, by means of doping or applying external hydrostatic pressure, the changes in the transition temperature are accompanied by spectral modifications. There are strong indications that the reduction in T c is correlated with a separation into nanoscale phases, which involve the oxygen atoms of the CuO 2 planes. In this work, modifications with doping in the Raman spectra of the La 2−x Sr x CuO 4 compound are presented, which show that spin or charge ordering is coupled with lattice distortions in the whole doping region.
2019
Riccardo Arpaia, 2, ∗ Eric Andersson, Alexei Kalaboukhov, Elsebeth Schröder, Edoardo Trabaldo, Regina Ciancio, Goran Dražić, Pasquale Orgiani, Thilo Bauch, and Floriana Lombardi † Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg, Sweden Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy CNR-IOM, TASC Laboratory, Area Science Park, Basovizza S.S. 14 km 163.5, I-34149 Trieste, Italy Laboratory for Materials Chemistry, National Institute of Chemistry, Hajdrihova 19, SI-1001 Ljubljana, Slovenia CNR-SPIN, University of Salerno, I-84084 Fisciano (SA), Italy (Dated: August 8, 2019)