  We study thermodynamic properties of the one-dimensional Heisenberg
ferrimagnet with antiferromagnetically exchange-coupled two kinds of spins 1
and 1/2. The specific heat and the magnetic susceptibility are calculated
employing a modified spin-wave theory as well as a quantum Monte Carlo method.
The specific heat is in proportion to $T^{1/2}$ at low enough temperatures but
shows a Schottky-like peak at mid temperatures. The susceptibility diverges as
$T^{-2}$. We reveal that at low temperatures the model is regarded as a
ferromagnet, while at mid temperatures it behaves like a gapped
antiferromagnet.
