Bulk magnetic and neutron diffraction data for the pyrochlore Yb2V2O7: Evidence for ferromagnetic coupling between Yb3+ and V4+ moments

Bulk magnetic data for the pyrochlore material Yb2V2O7 have been redetermined and compared with existing literature values. Susceptibility data from 300 to 77 K can be interpreted in terms of Curie-Weiss behavior above about 170 K, yielding the parameters Cm = 6.0 cm3 mole−1 K−1 and θc = −20 K. This θc is slightly more negative than values reported previously. The saturation moment at 4.2 K is 5.3 ± 0.1 μB, significantly greater than that reported previously. The magnetization versus temperature curve shows evidence for the ferromagnetic ordering of the V4+ sublattice at 73 K and the ferromagnetic ordering of the Yb3+ sublattice at about 30 K. The shape of the magnetization-temperature curve is most easily interpreted in terms of ferromagnetic coupling between the V4+ and Yb3+ sublattices. Neutron diffraction data at 7 and 100 K confirm the ferromagnetic model and yield a value of 1.7 ± 0.2 μB for the Yb3+ moment. This reduced moment (free ion = 4.0 μB) is consistent with crystal-field parameters found for the isostructural Yb2Ti2O7 which has a similar lattice constant.