Electronic and magnetic instability in Pr_0.65Ca _0.25Sr_0.1MnO₃

Electronic and magnetic instability in polycrystalline Pr _0.65Ca_0.25Sr_0.1MnO₃ manganite has been established from a systematic study of resistivity (ρ), magnetization (M) and specific heat (C). The sample shows a charge ordering transition at T_CO ∼ 200 K, an antiferromagnetic (AFM) ordering transition at T_N ∼ 175 K, a metal-insulator (MI) transition at T_MI ∼ 80 K and an unusual magnetic ordering transition at T_M ^* ∼ 45 K in the absence of magnetic fields. Though the C data do not show any anomaly at T_MI for MI transition, these illustrate a much smaller anomaly than expected one at T_M ^* and is suppressed by magnetic fields. This indicates that the unusual magnetic ordering in this sample is of canted, fluctuated or phase separation of AFM and ferromagnetic in nature which is established from the T-H phase diagram, as well as the thermal and magnetic hysteresis in ρ, M and C.