Exchange bias effect attributed to the spontaneous phase separation in polycrystalline Nd0.88Sr0.12CoO3

We observe the exchange bias effect in the low hole doped cobaltite Nd0.88Sr0.12CoO3. Training effect as well as systematic horizontal and vertical shifts of the hysteresis loops as a function of temperature and cooling field indicate the exchange bias effect. Temperature dependence of magnetization exhibits a peak at 28 K and an anomaly around ∼ 297 K below which zero-field cooled and field-cooled magnetizations deviate from each other. Strong frequency dependence in the ac susceptibility measurements indicates the spin freezing process at the low temperature peak which behaves like a spin-glass transition. The signature of exchange bias suggests the spontaneous separation between ferromagnetic (FM) and spin-glass like phases in the compound where FM domains or clusters have a single domain structure.