Specific heat at low temperatures and magnetic measurements inNd0.5Sr0.5MnO3andR0.5Ca0.5MnO3(R=Nd,Sm, Dy, and Ho) samples

We studied the magnetization as a function of temperature and magnetic field in the compounds ${\mathrm{Nd}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{MnO}}_{3},$ ${\mathrm{Nd}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},$ ${\mathrm{Sm}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},$ ${\mathrm{Dy}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},$ and ${\mathrm{Ho}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3}.$ Ferromagnetic, antiferromagnetic, and charge ordering transition in our samples agreed with previous reports. We also did specific-heat measurements with applied magnetic fields between 0 and 9 T and temperatures between 2 and 30 K in all five samples. Below 10 K the specific-heat measurements evidenced a Schottky-like anomaly for all samples. However, we could not successfully fit the curves to either a two level or a distribution of two-level-Schottky anomaly.