  The results of studies of Y$_{2}$Ti$_2$O$_7$ single crystals doped with
Er$^{3+}$ and Yb$^{3+}$ ions by means of electron paramagnetic resonance (EPR)
and dc-magnetometry are reported. EPR signals of the trigonal centers with the
characteristic hyperfine structure of Er$^{3+}$ or Yb$^{3+}$ ions were
observed. Field dependences of magnetization of single crystals for magnetic
fields directed along the crystallographic axes and temperature dependences of
magnetic susceptibilities were measured. Spin Hamiltonian parameters
($g$-factors and parameters of the hyperfine interaction) for Er$^{3+}$ and
Yb$^{3+}$ ions were obtained from analysis of experimental data. The registered
EPR spectra and magnetization curves were successfully reproduced by
simulations in framework of the crystal-field approach, in particular, with an
account for hybridization of ground 4f$^{13}$ configuration of Yb$^{3+}$ ions
with the charge transfer states.
