  We study the magnetic heat capacity of a series of magnetically ordered
Ce-based heavy fermion materials, which show an anomalous $T^3$ heat capacity
in excess of the phonon contribution in many materials. For compounds for which
magnon models have been worked out, we show that the local-moment magnon heat
capacity derived from the measured magnon spectra underestimates the
experimental specific heat. The excess heat capacity reveals increasing density
of states with increasing energy, akin to a pseudogap. We show that this
anomalous temperature-dependent term is not associated with proximity to a
quantum critical point (QCP), but is strongly correlated with $T_N$, indicating
the anomalous excitations are governed by the magnetic exchange interaction.
This insight may hold key information for understanding magnetically ordered
heavy fermions.
