  We have made a magnetic characterization of Nd0.5Sr0.5MnO3, Nd0.5Ca0.5MnO3,
Sm0.5Ca0.5MnO3, Dy0.5Ca0.5MnO3 and Ho0.5Ca0.5MnO3 polycrystalline samples.
Ferromagnetic, antiferromagnetic and charge ordering transitions in our samples
agree with previous reports. We also report specific heat measurements with
applied magnetic fields between 0 and 9 T and temperatures between 2 and 300 K
in all cases. Each curve was successfully fitted at high temperatures by an
Einstein model with three optical phonon modes. Close to the charge ordering
and ferromagnetic transition temperatures the specific heat curves showed peaks
superposed to the characteristic response of the lattice oscillations. The
entropy variation corresponding to the charge ordering transition was higher
than the one corresponding to the ferromagnetic transition. The external
magnetic field seems to have no effect in specific heat of the CO phase
transition.
