Distinct effects of Al3+ substitution at Cu-site and Al2O3 addition on step-like elastic anomalies and electron–phonon coupling constant in EuBa2Cu3O7−δ superconductors

Effects of Cd2+ substitution on elastic properties and step-like anomalies in Tl0.9Bi0.1Sr1.8Yb0.2Ca1−Cd Cu1.99Fe0.01o7− superconductors

“…Remarkably, the electron-phonon coupling constant increased with Cd substitution (Table 1) indicating that the substitution improves the strength of the electron-phonon coupling and may be conducive for Cooper pair formation in CuO 2 planes. Similar result was reported for Al 3 þ substituted EuBa 2 Cu 3 O 7 À δ [16], which showed λ increased with increasing Al 3 þ . In contrast, Sr substitution in DyBa 2 À x Sr x Cu 3 O 7 À δ [17] and Zn substitution in ErBa 2 Cu 3 O 7 À δ [42] showed decrease in electron-phonon coupling constant, λ BCS value.…”

“…This model is used to illustrate the extent of deviation of velocity or elastic moduli from the calculated anharmonicity curves at high temperatures. Previous works [14,16,17] such as for DyBa 2 À x Sr x Cu 3 O 7 À δ have shown that sound velocity in high temperature superconductors is dominated by lattice anharmonicity at lower temperatures but deviated at higher temperatures. A comparison between measured sound velocity data and calculated anharmonicity curve indicates that the appearance of step-like elastic anomalies at higher temperatures influenced the deviation of experimental data from calculated anharmonicity curves.…”

“…On the other hand, a number of studies have used Lakkad's anharmonicity model to explain and estimate the temperature dependence of velocity behavior or elastic moduli of RE123 and Tlbased systems [14][15][16][17][18]. This model is used to illustrate the extent of deviation of velocity or elastic moduli from the calculated anharmonicity curves at high temperatures.…”

Elastic moduli and step-like elastic anomalies in Ce-substituted Tl0.9Bi0.1Sr2−xCexCa0.9Y0.1Cu1.99Fe0.01O7−δ(x= 0–0.20) superconductors

“…On the other hand, the increase in u D , which is due to the increase in v m and the decrease in molar volume V a , confirms the overall increasing rigidity and stiffness with Ce substitution. [8] showed similar step-like elastic anomalies above 230 K. In the present work, the existence of the step-like elastic anomaly was suggested to be due to some form of oxygen ordering taking place in TlÀO planes. A similar explanation was reported for other Tl1212 samples such as TlSr 2 (Ca 1¡x Pr x )Cu 2 O 7¡d , [13] TlSr(Sr 1¡x Y x )Cu 2 O 7 [12] and TlSr 2 (M 1¡x Y x )Cu 2 O 7 (M D Ca, Sr), [11] where it was suggested that the step-like elastic anomaly reflects the possibility of structural distortion of TlÀO planes related to the existence of short-range oxygen ordering in TlÀO (3) superstructures.…”

Effect of small oxygen deficiency on the para-coherent transition and 2D–3D crossover in untwinned YBa2СuзО7−δ single crystals

“…The model high temperature HTSC remains the ReBa 2 Cu 3 O 7−ı (Re = Y or rare earth ion) system. Defects, the composition or external means such as pressure can be significant for tuning the properties of ReBa 2 Cu 3 O 7−ı [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. For example, HoBa 2 Cu 3 O 7−ı is paramagnetic in the normal state, whereas YBa 2 Cu 3 O 7−ı is not (refer to [8] and references therein).…”