Exchange interactions ofYb3+ions inYbxY1−xBa2Cu3Oy

Abstract

The EPR spectrum of ${\mathrm{Yb}}^{3+}$ ions in ${\mathrm{Yb}}_{x}{\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$ $(x=1.0,$ 0.5) is studied as a function of temperature. In the oxygen-deficient superconducting phase, the ${\mathrm{Yb}}^{3+}$ EPR spectrum comprises a broad EPR line described by a rhombic g tensor and anisotropic linewidths along the principal axes. Analysis of the EPR linewidth provides an estimate for the effective isotropic exchange interaction, ${J/k}_{B}\ensuremath{\approx}0.3\mathrm{K},$ between ${\mathrm{Yb}}^{3+}$ ions, indicating that the magnetic ordering of the ${\mathrm{Yb}}^{3+}$ sublattice is determined by the interplay between the short-range exchange interactions and the long-range dipole-dipole interactions.