CRYSTAL-FIELD PHENOMENA IN RARE-EARTH CUPRATES

We present some results pertaining to the crystal field (CF) interacti ons in high T-c rare earth (RE) cuprates and related layered compounds and manifestations of their impact on magnetic properties. We show th at the widely disputed specific-heat and susceptibility data in PrBa2C u3O7 can be interpreted consistently in terms of the standard CF theor y for Pr3+ based on the CF parameters extracted from the inelastic neu tron scattering spectra via the superposition model. The CF-induced el ectric quadrupoles are shown to lead to thermal expansion anomalies in Sm2CuO4 and REBa(2)Cu(3)O(7) compounds. We examine general conditions for an Ising-like behaviour of the RE subsystem. We conclude that suc h a behaviour may possibly occur in cuprates containing Tb, Dy and Ho owing to the special nature of low-lying 4f states imprinted by the CF interaction.