The magnetic susceptibility chi, the absorption and luminescence spectra, a
nd the Verde constant V along different crystallographic axes of the rhombi
c crystal TbAlO3 have been investigated experimentally in the temperature i
nterval 78-300 K. It is found that, in contrast to the magnetic susceptibil
ity chi measured along the [110] axis, the Verde constant V varies in inver
se proportion to the temperature in the given range. It is shown that this
temperature dependence of the Verde constant measured along the [110] axis
is connected with the absence of a contribution to the Faraday rotation of
the van Vleck mechanism (in an external field H) of "mixing" of the states
of the rare-earth ion Tb3+. From a comparison of the optical and magnetic m
easurements, we have determined the wave functions and magnitudes of the St
ark intervals between the lower Stark sublevels for the F-7(6) ground multi
plet of the Tb3+ ion in the ortho-aluminate TbAlO3. (C) 1999 American Insti
tute of Physics. [S1063-7834(99)02811-7].