Nd_(0.67)Sr_(0.33) MnO_y(y<3.0)中的自旋相关电致电阻效应

Spin-dependent electroresistance in Nd_(0.67)Sr_(0.33) MnO_y(y<3.0)

用固相反应法制备系列Nd0.67Sr0.33MnOy(y=3.00—2.80)多晶样品.样品输运性质表现出自旋相关电致电阻特征.对氧含量等于化学计量样品,在测量温度范围内电阻不随负载电流变化,I-V曲线符合线性欧姆定律.对氧含量低于化学计量样品,当高于某一特征温度时,电阻变化符合线性欧姆定律;但低于这一特征温度时,电阻大小与负载电流有关,I-V曲线偏离线性规律;在绝缘体-导体相转变点附近,样品电阻随负载电流增大而迅速减小,表现出巨大电致电阻效应.对于y=2.85样品,当电流从1μA增加到30μA时,电致电阻接近80%.这种自旋相关的电致电阻行为与氧含量和界面有很大关系.

Spin-dependent electroresistance （ER） was observed in polycrystalline Nd0.67 Sr0.33 MnOy （ y = 3.00, 2.95, 2.90, 2.85, 2.80） samples, which were synthesized by solid-state reaction. For the sample with stoichiometry y = 3.0, the I-V characteristic shows ohmic linearity over the whole range of measuring temperature. For the samples with oxygen-deficiency, i.e. y 〈 3.0, I-V curve is linear when temperature is above a certain point, similar to the case of y = 3.0. However, the electric resistance strongly depends on load current, decreasing remarkably with increasing current load when temperature falls below the critical temperature. For the sample of y = 2.85, the ER ratio reaches 80 % when the load current increases from 1 to 30 μA. The spin- dependent ER effect should be strongly related with the oxygen-deficiency and grain boundary effect.