Abstract
The effects on the rare-earth crystal-field-splitting schemes of incorporation of large spin-orbit coupling (5d) ions, such as Ir4+, into the rare-earth pyrochlores are largely unknown. We report on the preparation, specific heat, magnetization, and inelastic neutron-scattering study of Er2Ir2O7 pyrochlore.
An anomaly in specific heat and bifurcation of zero-field cooled and field cooled magnetization indicates an ordering of the Ir sublattice below 140 K, in good agreement with other rare-earth pyrochlore iridates. The Er sublattice ordering below 2 K can be considered short range as well, following the development of specific-heat and magnetization data down to low temperatures.
The inelastic neutron scattering allowed us to unambiguously determine the crystal-field (CF) eigenenergies and parameters of Er2Ir2O7, which are dictated dominantly by nearest-neighbor anions (the oxygen cage around the Er cation). The influence of the magnetic iridium cations on the erbium CF scheme is rather moderate despite the strong spin-orbit coupling expected in a 5d metal, which is evident when comparing the energy spectra of this iridate and other 3d- or 4d-metal containing erbium pyrochlores.
The determined CF parameters were subsequently utilized for calculations of magnetization and specific-heat CF contributions, leading to an excellent agreement with experimental data.