Magnetic behavior of 3d dopants in superconducting REBa2Cu3-x57FexO7+δ (RE = Dy, Er)

Moessbauer studies on 57Fe-doped superconducting REBa2Cu3O7+δ (RE = Er, Dy) were made as a function of temperature for x=0.15 and 0.30. The magnetic behavior of the 3d dopants, which mainly occupy Cu(1) sites, undergoes antiferromagnetic ordering which is coexistent with superconductivity at low temperature. The dimensionality of the magnetic interaction changes from 2D to 3D when the rare earth changes from Er to Dy. The line-widths of the Moessbauer subspectra are characteristic of magnetic fluctuation behavior in the vicinity of a phase transition. Combining these results with those of Fe-doped Y-123 (pseudo 1D) and Gd (3D), the magnitude of the rare earth moments appears to be strongly correlated with the dimensionality of the magnetic interaction of Fe dopants in these compounds. However, the Moessbauer spectrum for 155Gd in GdBa2Cu2.85Fe0.15O7+δ (TN(Fe)∝14 K) shows no magnetic order at 4.9 K. (orig.)