【摘要】 我们在不同的降温速率下得到了若干La0 .7Ca0 .3Mn1-xCrxO3-δ(x =0 .0 0 ,0 .0 8)多晶样品 ,对其进行了XRD、电阻 温度关系和磁化强度 温度关系的测量 .实验发现 ,随降温速率的增大 ,LCM系列样品的电阻变大 ,电阻峰温度移向低温端 ,磁化强度值变小 ,金属 绝缘体转变依然很陡峭 ,而LCMC系列样品也兼有这些现象 ,前两者的程度更大些 ,后者较为平缓 ,另外还出现了电阻的双峰 .归结原因 ,我们认为在制备过程中随降温速率的不同 ,样品中会有不同程度的氧空位存在 ,利用双交换的减弱和样品中氧的分布不均匀产生的相分离解释了有关现象 .通过本实验可知 ,改变降温速率也是调节样品中氧含量的一种有效的方法 .更多还原

【Abstract】 A series of La\- 0.7 Ca\- 0.3 Mn\- 1- x Cr\- x O\- 3- δ ( x =0.00, 0.08) polycrystalline samples have been prepared with different cooling speeds. A careful study in the magnetic and electrical transport properties has been carried out by the measurements of magnetization and resistivity. It was found that, with the augmentation of cooling speed, the resistivity of all samples is augmented, the temperature site of resistivity bumps is declined, besides LCMC samples is characterized by double bumps. We suggest the cooling speed could effect on oxygen deficiency of samples. It indicates that cooling speed may be a potent way in changing oxygen content of samples.更多还原