Magnetic properties of the quaternary oxides Ba(2)LnTaO(6) (Ln = Y or lanth
anides) are reported. Their powder x-ray diffraction measurements and Rietv
eld analysis show that they have an ordered perovskite structure and are mo
noclinic (Ln = La-Tb) with space group P2(1)/n or cubic (Ln = Y, Dy-Lu) wit
h space group Fm3m. Magnetic susceptibilities of Ba(2)LnTaO(6) were measure
d. All compounds in this work are paramagnetic down to 5 K. Ba2EuTaO6 and B
a2SmTaO6 show Van Vleck paramagnetism; their spin-orbit coupling constants
are determined to be 331 cm(-1) and 287 cm(-1), respectively. Eu-151 Mossba
uer measurements for Ba2EuTaO6 were carried out at 12, 100, 200 and 300 K.
The Eu ion is in the trivalent state, and the symmetry of the Eu site is di
storted from the octahedral symmetry. The Debye temperature of Eu3+ was det
ermined to be 335 K from the temperature dependence of the absorption area
of intensity curves.