The magnetic properties of R in Pb2Sr2(R/Ca)Cu3O8 (R = HO and Er)

The electronic behavior of the rare-earth ion (R) in the Pb based superconductors Pb2Sr2(R1−xCax)Cu3O8, for R = Er (x = 0, 0.5) and Ho (x = 0), has been analyzed by inelastic neutron scattering. Sharp, well-defined transitions of magnetic origin have been observed for the parent R = Er and Ho (x = 0) compounds. Peaks, determined to be of magnetic origin, have been assigned to crystal-field (CF) transitions within the Russell-Saunders ground multiplet. These results have been modeled using a crystal-field hamiltonian that includes intermediate-coupling and spherical-tensor techniques. The CF potential was determined for tetragonal symmetry. The calculated parameters are similar to those determined for similar R in the RBa2Cu3O7 compounds. The results of the crystal-field analyses for the parent compounds are used to calculate the expected rare-earth contributions to the magnetic susceptibility, and compared to experimental data where available. In contrast to the data on the parent compounds, the spectra obtained from the superconductor Pb2Sr2Er0.5Ca0.5Cu3O8 show only very broad features. This broadening is attributed to chemical disorder rather than to an electronic effect.