Neutron time-of-flight spectroscopy has been employed to study the crystal-
field interaction in the pyrochlore titanate Ho2Ti2O7. The crystal-field pa
rameters and corresponding energy-level scheme have been determined from a
profile fit to the observed neutron spectra. The ground state is a well sep
arated E-g doublet with a strong Ising-like anisotropy, which can give rise
to frustration in the pyrochlore lattice. Using the crystal-field paramete
rs determined for the Ho compound as an estimate of the crystal-field poten
tial in other pyrochlore magnets, we also find the Ising type behavior for
Dy. In contrast, the almost planar anisotropy found for Er and Yb prevents
frustration, because of the continuous range of possible spin orientations
in this case. (C) 2000 American Institute of Physics. [S0021- 8979(00)22908
-3].