  In many cases, the critical-state theory can be treated as a suffi ciently
accurate approximation for the modelling of the magnetic properties of
superconductors. In the present work, the magnetostrictive hysteresis is
computed for a quite general case of the modified Kim-Anderson model. The
results obtained reproduce many features of the giant magnetostriction
(butterfly-shaped curves) reported in the literature for measurements made on
single-crystal samples of the high-temperature superconductor
$Bi_2Sr_2CaCu_2O_8$. It is shown that addition of a contribution to the
magnetostriction in the superconducting state which is of similar origin as in
the normal state, offers a broader phenomenological interpretation of the
complex magnetostriction hysteresis found in such heavy-fermion compounds as
$UPt_3$, $URu_2Si_2$ or $UBe_{13}$.
