  The Pr(1-x}CaxMnO3 system exhibits a ferromagnetic insulating state for the
composition range x<0.25. A metallic ferromagnetic state is never realized
because of the low hole concentration and the very small averaged A-site cation
radius. In the present study, the nature of the magnetic excitations at low
temperature has been investigated by specific heat measurements on a
Pr0.8Ca0.2MnO3 single crystal. The decrease of the specific heat under magnetic
field is qualitatively consistent with a suppression of ferromagnetic spin
waves in a magnetic field. However, at low temperature, the qualitative
agreement with the ferromagnetic spin waves picture is poor. It appears that
the large reduction of the specific heat due to the spin waves is compensated
by a Schottky-like contribution possibly arising from a Zeeman splitting of the
ground state multiplet of the Pr{3+} ions.
