Exchange bias associated with phase separation in the perovskite cobaltite La1-xSrxCoO3

We report the observation of exchange bias phenomena in the hole-doped perovskite cobaltites La1-xSrxCoO3 (x=0.12, 0.15, 0.18, and 0.30) in which a spontaneous phase separation occurs. When the La1-xSrxCoO3 samples are cooled in a static magnetic field through a freezing temperature, the magnetization hysteresis loops exhibit both horizontal and vertical shifts. We also observed training effect of the exchange bias, which can be interpreted by a spin configurational relaxation model. Moreover, exchange bias in La1-xSrxCoO3 is strongly dependent on the measuring field and the cooling field due to the influence of magnetic field on the relative proportion of the coexisting phases. These results suggest that the intrinsic phase inhomogeneity in a spontaneously phase-separated system may induce an interfacial exchange anisotropy.