Crystal field phenomena in rare earth cuprates

Abstract

We present some results pertaining to the crystal field (CF) interactions in high T c rare earth (RE) cuprates and related layered compounds and manifestations of their impact on magnetic properties. We show that the widely disputed specific-heat and susceptibility data in PrBa 2Cu 3O 7 can be interpreted consistently in terms of the standard CF theory for Pr 3+ based on the CF parameters extracted from the inelastic neutron scattering spectra via the superposition model. The CF-induced electric quadrupoles are shown to lead to thermal expansion anomalies in Sm 2CuO 4 and REBa 2Cu 3O 7 compounds. We examine general conditions for an Ising-like behaviour of the RE subsystem. We conclude that such 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.