Local structure in single crystals of La-based high T_ccuprates

63Cu-NMR study on High-TcSuperconductor La2−xBaxCuO4

“…From these two observations, we can conclude that the local structure is always in accordance with the averaged structure in LBCO. This makes a clear contrast to LSCO, where the existence of the local structure of LTT is reported in samples possessing the averaged structure of LTO [8,9]. In the present case of LBCO, a great disparity between the ionic radii of Ba +2 and La 3+ may stabilize the spatially-coherent LTT structure to make the phase boundary between LTT and LTO distinct.…”

“… Q was determined to be 32.2 and 32.8 MHz for x=0.08 and 0.10 respectively from the -dependence of H res [8,9]. As shown schematically in Fig.…”

“…So far, the stripe order in La-based high-T C cuprates has been intensively studied by many experimental techniques [2,3,4] and the existence of the strong stabilization effect on the stripe order by the structure of so-called low-temperature tetragonal phase (LTT) has been confirmed [5,6]. Furthermore, it has been reported that the local structure of LTT, which does not have a spatial coherence and hence cannot be detected by scattering techniques, appear in some conditions of temperatures or dopant concentration [7][8][9][10][11]. This incoherent local structure also shows a slight pinning effect on the stripe order if weaker than the LTT structure with the spatial coherence.…”

“…Actually, the LTT phase appears in either case when hetero ions with radius larger than La 3+ such as Ba 2+ or smaller such as Nd 3+ are substituted, and its appearance mechanism cannot be simply explained in terms of the epitaxial distortion between the CuO 2 plane and the block layer consisting of the layered structure of La-based high-T C cuprates [12,13]. As for the local structure of the LTT phase, its existence itself is still in controversy [7][8][9][10][11]14]. The purpose of this paper is devoted to the microscopic detection of the local structure of LTT phase in La 2x Ba x CuO 4 (LBCO) and to find out the appearance condition of the phase.…”

First-principles study on lattice instabilities and structural phase transitions in Ba doped La2CuO4

“…Generally, the tilting angle is larger in the Ba-contained compounds than in the Sr contained compounds [29]. This could be a reason for the fact that superconductivity is completely suppressed in LBCO, while only partly in LSCO.…”