WAVE-VECTOR DEPENDENCE OF INTERMULTIPLET TRANSITIONS IN EUBA2CU3OX(X=6.1 AND 7) - AN INELASTIC NEUTRON-SCATTERING STUDY

The momentum-transfer (Q) dependence of inelastic-neutron-scattering d ipolar and higher multipolar CEF split transitions from EU3+ in EuBa2C u3Ox (x=6.1 and 7) are calculated and, where possible, compared with t he observations. For the transitions between the F-7(0) and the F-7(4) CEF split multiplets, distinct differences in the Q dependence betwee n 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 transition s to a model crystal-field splitting scheme in order to determine the eigenfunctions and corresponding energy levels as input for the e-depe ndence calculations. We found an unusually low-energy separation betwe en the F-7(0) ground state and the first excited F-7(1) multiplet whic h is well understood due to two effects. First, the strong CEF interac tion mixes the wave functions of states between different multiplets w hich leads to a reduction of the energy separation. Second, the free-i on parameters are slightly reduced, which could be understood by assum ing a linear behavior with the average distance of the nearest-neighbo r shell.