Exchange bias and spin glassy behavior in low doped La1-xSrxCoO3 cobaltites

We present an extensive study of the exchange bias properties and glassy behavior in low-doped La1-xSrxCoO3 cobaltites. The temperature dependences of the dc magnetization and ac susceptibility indicate that the spin glass state exists even at high magnetic fields. The field-cooled magnetic hysteresis loops exhibit both horizontal and vertical shifts. The vertical shift decreases with increasing the measuring field and approaches zero around 40 kOe, while the horizontal shift still exist even at 80 kOe. It is suggested that these two shifts may have different origins. The cooling- field dependence of the training effect was measured and analyzed by the power law and a spin configuration relaxation model. The results show that the suppression of the spin glass state region with increasing cooling fields plays the most important role in the decrease of the exchange bias field. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3123812]