Unravelling the role of Cu-O chain length on the superconducting properties of SmBa ₂ Cu ₃ O _{6 + δ} via Al doping and clustering

Abstract

The superconducting properties of the SmBa2Cu3O 6+δ superconductor change dramatically upon oxidation. The driving force for these changes is still under debate because many concomitant structural changes occur. In order to highlight the specific role of Cu-O chain ordering on the rise of superconductivity in this system, Al-doped SmBa2Cu3O 6+δ samples have been examined, having equal aluminium and oxygen concentration and nearly the same structure but different mean length of Cu-O chain fragments. For the first time, it is clearly shown that, keeping all the other structural properties unchanged, the local increase of the chain length determines a significant enhancement of the superconducting properties, i.e. TC and Meissner fraction.

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

“…Elemental substitutions in place of Cu i.e. REBa 2 (Cu 1−x M x ) 3 O 7−ı have been reported to show slightly different effects; substitution of M = Al 3+ and Ga 3+ was suggested to go into Cu-O chains while substitution of M = Zn 2+ and Ni 2+ was suggested to occupy CuO 2 planes of RE123 compounds [19][20][21][22][23][24][25]. The former does not affect T c drastically for low dopant concentrations compared to the latter.…”

Effects of Slight Non-Stoichiometry in Sm-Ba-Cu-O Systems on Superconducting Characteristics

“…In the last case, the length of Cu-O(1) chains decreases. The dependence of the critical temperature on the length of the Cu-O(1) chains and processing temperature is well known [22][23][24]. These effects together determine the superconducting properties of A samples, e.g.…”

Effect of Local Disorder on the Transport Properties of Al-Doped SmBa2Cu3O6+δ Superconductors

“…The presence of this kind of disorder could help to shed light on some nontrivial effects occurring in SmBa 2 Cu 3-x Al x O 6+δ samples such as the increase of T C and Meissner fraction by varying the Al distribution within the Cu1 sites while keeping x and δ constant (i.e., the total charge carrier concentration 19 in SmBa 2 Cu 2.85 Al 0.15 O 6.98 ), as well as the appearance of superconducting diamagnetic fluctuations above T C in the same compound.…”

“…In fact, it is possible to produce samples with the desired charge carriers concentration (tuning x and δ) and spatial extension of potential fluctuations within the Cu2-O2/3 planes using appropriate annealing cycles. 17,19 …”

“…19,20 At fixed Al and O concentrations (i.e., total hole concentration), the Cu-O ordering on the nanometric scale deeply affects the superconducting properties of the material, i.e., T C and the Meissner fraction. 19 Moreover, Al clustering induces the rising of superconducting diamagnetic fluctuations above T C exhibiting unconventional Ginzburg-Landau character.…”