Precursor superconducting diamagnetism in YBa₂Cu₃O_7−δwith in-plane or intercalated magnetic impurities

Abstract

The magnetization around the superconducting transition was measured in YBa 2 Cu 3 O 7−δ with magnetic impurities in the CuO 2 layers (Cu substituted by Zn or Ni) or between them (Y substituted by Gd or Pr). While some of these impurities have an important effect on the superconducting transition temperature (T c ), the precursor diamagnetism observed above T c is not appreciably affected. This result contrasts with recent observations in a conventional BCS superconductor (La), in which the precursor diamagnetism was found to increase several orders of magnitude with the addition of a small amount (a few atomic per cent) of Gd or Pr magnetic impurities.

Magnetic field dependence of the precursor diamagnetism in La superconductors with magnetic Pr impurities

“…[11]). This is in fact the case of high-T c cuprates: recent measurements [12] have shown that the fluctuation diamagnetism of optimally-doped YBa 2 Cu 3 O 7−δ is not appreciably affected by the presence of magnetic impurities (both in the CuO 2 planes or intercalated between them). In striking contrast, the measurements in lanthanum with diluted magnetic (Pr) impurities presented in Ref.…”

“…(For a recent theoretical work on this issue see, e.g., [11].) This is in fact the case with high-T c cuprates: recent measurements [12] have shown that the fluctuation diamagnetism (FD) of optimally doped YBa 2 Cu 3 O δ − 7 is not appreciably affected by the presence of magnetic impurities (either in the CuO 2 planes or intercalated between them). In striking contrast, the measurements in lanthanum with diluted magnetic (Pr) impurities presented in [13] have shown an important enhancement of FD, that is observed to be considerably larger than the theoretical results for three-dimensional isotropic superconductors [5,6,[14][15][16][17][18][19].…”