The perovskite manganite families Gd_1−xCa_xMnO₃ and Nd_1−xCa_xMnO₃ , where 0 ⩽ x ⩽ 1 (hereafter
GCMO and NCMO, respectively) were screened for the prospect of a strong magnetocaloric effect by
experimentally determining magnetic transition entropies. Magnetic transitions in the temperature
range of 5–400 K were investigated in external fields up to 5 T. Entropy-based refrigerant capacities
and magnetic hysteresis losses were also taken into account. The evolution of the magnetocaloric
performance estimates versus the Ca concentration, x, was found to be qualitatively identical to that
reported in Pr_1−xCa_xMnO₃ (PCMO). In line with this analogy, the highest estimated magnetocaloric
performance of GCMO and NCMO was found in the low-x region, below the temperature of 140 K.
Here the entropy-based figures of merit were comparable to the best magnetocaloric transitions seen
in e.g. PCMO and Gd₅Si₂Ge₂ . The low magnetic hysteresis, dielectricity and tunability by forming
solid solutions with other manganites add to the potential of GCMO and NCMO as low-temperature
magnetic refrigerants. At higher temperatures their magnetocaloric applicability is very limited at
best, but a side-by-side comparison of GCMO, NCMO and PCMO can also be seen as a valuable
theoretical instrument for understanding the general magnetic phase diagram of low bandwidth
manganites.