The magnetostriction of a single-crystal sample of the metastable, fer
roelectric, ferroelastic, orthorhombic beta' phase of Tb2(MoO4)3 has b
een measured at 78 K in pulsed magnetic fields up to 150 kOe. In field
s from 80 to 100 kOe directed along the [100] axis, a strain on the or
der of 6 X 10(-3) arises because of a switching of the spontaneous ele
ctric polarization.