Magnetic Properties of Oxygen Deficient Y0.33Sr0.67CoO3-δ

We studied magnetic properties of perovskite-type Y 0.33 Sr 0.67 CoO 2.614 and Y 0.33 Sr 0.67 CoO 2.707 prepared under different sintered temperatures at 1250 • C and 1100 • C, respectively.A dc magnetization jump associated with a large thermal hysteresis around 180 K was found in Y 0.33 Sr 0.67 CoO 2.614 , which indicates a kind of magnetic memory effect.On the other hand, Y 0.33 Sr 0.67 CoO 2.707 shows a larger magnetization with a small magnetization jump around 200 K and lower Curie temperature than those of Y 0.33 Sr 0.67 CoO 2.614 .Rich Co 3+ ions in the low temperature sintered Y0.33Sr0.67CoO2.707possibly introduce large magnetization and high magnetization jump temperature.This may be coming from a surface/volume effect of Co 3+ ions appearing in the polycrystalline sample prepared at low temperature.The ferromagnetism resulted from the different surface/volume ratio contributes to a part of magnetization and may result in the change of the Curie temperature.