Wave-vector dependence of intermultiplet transitions inEuBa2Cu3

Abstract

The momentum-transfer (Q) dependence of inelastic-neutron-scattering dipolar and higher multipolar CEF split transitions from Eu 3ϩ in EuBa 2 Cu 3 O x ͑xϭ6.1 and 7͒ are calculated and, where possible, compared with the observations. For the transitions between the 7 F 0 and the 7 F 4 CEF split multiplets, distinct differences in the Q dependence between the different excitations is anticipated. Some of these transitions are expected to have relatively strong dipolar contributions. In order to perform these calculations, it was necessary to fit the transitions to a model crystal-field splitting scheme in order to determine the eigenfunctions and corresponding energy levels as input for the Q-dependence calculations. We found an unusually low-energy separation between the 7 F 0 ground state and the first excited 7 F 1 multiplet which is well understood due to two effects. First, the strong CEF interaction mixes the wave functions of states between different multiplets which leads to a reduction of the energy separation. Second, the free-ion parameters are slightly reduced, which could be understood by assuming a linear behavior with the average distance of the nearest-neighbor shell.