为了提高 La0．7 Sr0．3 MnO 3的低场磁电阻效应，将样品进行了磁场退火处理.实验结果表明，磁场退火并没有改变样品的磁矩，但对其磁各向异性产生了较大的影响.与零磁场下退火的样品相比，磁场退火样品的磁电阻明显提高.这种增强效应在低磁场下更加明显，在0．1 T 的外磁场下，磁退火样品的磁电阻比零场退火的提高了140％.利用自旋极化隧穿机制解释了这种增强的磁电阻效应.
Polycrystalline perovskite La0.7 Sr0.3 MnO 3 was annealed under magnetic field in order to increase the low-field magnetoresistance effect.The experimental results show that the magnetic annealing would not affect the magnetic moments but remarkably change the magnetic anisotropy of the sample.Compared with the per-ovskite without magnetic annealing,the magnetic-annealed La0.7 Sr0.3 MnO 3 exhibits large magnetoresistance effect,which can be more obviously observed in low magnetic field.At room temperature,a 140% enhancement of magnetoresistance response at 0.1 T was observed in the magnetic-annealed sample,which can be explained with the mechanism of spin-polarized intergrain tunneling.
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