Electrical conductivity of YBa2Cu3O7-δ single crystals under conditions of anionic ordering in Cu(1)O1-δ layers

Abstract

The influence of thermocycling annealing processes on the oxygen ordering degree (order parameter) in YBa2Cu3O7-δ single crystals has been studied. It has been shown that an increase in the critical onset temperature of the transition to the superconducting state during thermocycling annealing procedures is consistent with the decrease of the σс/σаb parameter. This fact indicates a redistribution of the electronic density between the structurally inhomogeneous Cu(2)O2 and Cu(1)O1-δ planes, due to the formation of oxygen long-range order in the O(4)–Cu(1)–O(4) linear groups along the (b) crystal structure axis of the unit cell, and elimination of oxygen defects in the square nets of the Cu(2)O2 planes. The existence of the critical value of the conductivity anisotropy σс/σаb, below which its behavior does not correlate with the change of Тс, has been confirmed. In this case an increase in Тс and orthorhombic distortion of the crystal structure during isothermal annealing are caused by the amplification of the “interlayer” interaction between the Cu(2)О2 and Cu(1)О1-δ planes. As a result, the contribution of the Cu(1)О1-δ chain layers to the electron state density at the Fermi level increases. These layers can acquire superconducting properties due to tunneling of Cooper pairs from the Cu(2)О2 planes resulting in the formation of the induced superconductivity in these planes.

Transport Properties of Ferromagnet/Superconductor and Superparamagnet/Superconductor Heterostructures Based on Ni/YBCO

“…Besides, such important parameters of the system as the London penetration depth (150-300 nm), the energy gap (20−25 MeV), and the critical magnetic field (250 T) were previously determined [2]. At the moment, it is relevant to study the dependence of the critical temperature on the composition and proportion of alloying materials in YBCO [3][4][5][6], defects, and features of its crystal lattice [7][8][9]. Likewise, the work is also actively underway to develop a universal theory of high-temperature superconductivity, including the basis of the YBCO system [10,11].…”