Plausible d-wave cuprate superconductivity: Muon-spin-relaxation studies of RBa2Cu3O7-delta vortex states

The rare-earth (R) magnetism and grain-size dependencies of magnetic field distributions in RBa2Cu3O7-delta (RBCO) vortex states have been studied. A maximum-entropy technique has been applied to transverse field muon-spin-re laxation data of several polycrystalline cuprate superconductors. The main vortex signals for R = Er, Gd, and Ho reveal signs of two peaks in the fiel d distribution below the applied field (B-ext=1 kOe) as predicted for d-wav e superconductivity. For the RBCO (R = Er, Gd, Ho, Eu, Y) vortex states, we have confirmed low-field tails in the field distributions well below B-ext . The low-field tail may be caused by magnetic frustration in the vortex st ate or possible CuO-chain superconductivity below 25 K. Any interpretation of these (magnetic) vortex anomalies should comprise unconventional non-Bar deen-Cooper-Schrieffer-like fundamental properties of the cuprate vortex st ates. (C) 1998 American Institute of Physics.