X-ray absorption studies of La2-x(Ba,Sr)xCuO4 high-Tc superconductors

Origin ofTcsuppression due toR=Eu, Nd, and Pr in superconducting (La1Arai1, Iwata2, Umezawa3 1996Phys. Rev. B7210View full textAdd to dashboardCite

“…This prediction is supported by the following experimental fact that when La 3ϩ ions are replaced by Sr 2ϩ or Ba 2ϩ ions which have larger ionic radii than that of La 3ϩ , the distance of Cu( P)-O(A) shrinks although the lattice parameters a and c increase. [24][25][26] The fact that Eu elements which have the smallest ion radius in the three rare-earth elements suppress T c most severely can be understood by the strongest reduction of ⌬V A as mentioned above. Therefore, it follows that Eu substitution makes the distance of Cu( P)-O(A) expand the most of the three R ions.…”

Defect and Electronic Structures of Calcium‐Doped Lanthanum Cuprate

“…Figures 3(a) and (b) are the corresponding k 3 -vs-k graphs. The DW factors (mean square displacements, ⌬ 2 , in 12 3.25 Experiment, Akthar et al 12 3.25 Fig. 2.…”

“…This shift is evident from the fact that the distance to one of the Cu atoms is significantly smaller than the distance to the other Cu atoms. Also, the distances to the O(1) and O (2) In Table IV, computed interatomic distances for the MЈ La defects are compared to distances that have been derived from EXAFS measurements and atomistic modeling that has been reported for M ‫ס‬ Sr and Ba by Akthar et al 12 and for M ‫ס‬ Ca from this work (see later discussion). As was done in this paper, the atoms are grouped into four sets: four O(1) atoms, a single apical O(2) atom, four equatorial O(2) atoms, and four Cu atoms.…”

Characterization of the Local Layer Structure of a Narrow Wall in a Surface Stabilized Ferroelectric Liquid Crystal Using Synchrotron X-Ray Micro-Diffraction

“…EXAFS spectroscopy has emerged as a unique technique for the determination of the local structure of a particular atom, because the environment of a particular element can be measured irrespective of the structural or chemical complexity of the material. EXAFS spectroscopy has been used to determine the local environment of different cations in La 2−x (Ba, Sr) x CuO 4 [31][32][33] and Bi-based high-T c materials [30]. EXAFS spectroscopy has previously been used for the determination of the local environment of Cu in YBa 2 Cu 3 O 7−δ [34][35][36][37].…”

“…The results obtained from the analyses of these data show that the average structural parameters (table 1) In addition, we found relatively high Debye-Waller factors (DW F s) for the Cu-Ba shells in YBa 2 Cu 3−x Sb x O 7−δ , indicating a high degree of disorder for the Ba atoms. It is worth mentioning that the coordination numbers and Debye-Waller factors strongly correlate with each other [30,33]; therefore, in one set of data the coordination numbers are kept fixed at their preset values, for these results the Debye-Waller factors are relatively high for the Cu-Ba shells. When coordination numbers are refined, we found that there is a relatively large decrease of Ba around Cu, when compared with other ions (in table 1 the values in brackets are those obtained with refined coordination numbers).…”