Specific heat of Nd_1-xSr_xMnO₃ (x ∼ 0.5)

The specific heat of the single crystal of Nd_1-xSr_xMnO₃ (x ∼ 0.5) has been measured at 20 K < T < 280 K in H < 5 T. Two specific heat anomalies are observed at T_C ∼ 255 K and T_N ∼ 157 K (x = 0.5) and 164 K (x = 0.5 + δ with δ ≃ 0.002). The former transition is attributed to the ferromagnetic order of Mn³⁺ and Mn⁴⁺ spins and the latter the charge and orbital orders at the ferromagnetic-antiferromagnetic (AF) transition. Double peak structure is seen at T_N in the sample with x = 0.5 + δ, but not for x = 0.5. These two peaks are related to the phase segregation of the CE and A-type AF order phases in narrow x range of 0.5 < x < ∼0.52.