Magnetic order and crystal field in Dy2Ru2O7 and Yb2Ru2O7

Abstract The magnetic properties of R2Ru2O7 pyrochlore compounds (R=Yb, Dy) were studied using specific heat down to 0.4 K and bulk magnetic measurements. These two rare-earth elements were chosen to demonstrate the effect of Ru–R exchange interaction on R magnetic sublattice, in two cases of anisotropy: axial in Dy and planar in Yb. Dy2Ru2O7 undergoes a second order transition to a fully ordered state at 1.85 K with no signs of the spin-ice state. In Yb2Ru2O7 the Yb sublattice orders gradually around 8 K due to the Ru molecular field and no further transition is observed down to 0.4 K. Including the Ru molecular field at the R site in calculations based on crystal field parameters known from titanates R2Ti2O7, allowed us to interpret experimental data.