摘要
采用溶胶凝胶法制备了系列多晶CMR材料La0.7Ca0.3Mn1-xCuxO3(x=10%,14%,15%,16%,18%,20%)。在77K^350K温度范围内测量了样品的电阻率及磁电阻大小。实验结果发现,系列样品在整个测温范围内均表现出绝缘相行为,未出现金属相到绝缘相的M-I转变。对系列样品的ρ-T曲线进行lnρ-T-(1/4)关系拟合,发现掺杂量为x=10%、14%两个样品在整个温区内的lnρ-T-(1/4)关系基本呈线性,掺杂量为15%、16%、18%及20%四个样品在较高温区的lnρ-T-(1/4)关系亦基本呈线性。采用Mott等人提出的小极化子VRH模型进行了解释。实验中还发现,系列样品的磁电阻在整个测温范围内基本呈现隧穿磁电阻行为,基于我们采用Monte Carlo模拟方法提出的隧穿磁电阻模型,对样品的磁电阻行为进行了解释。
A series of polycrystal bulk samples of La0.7Ca0.3Mn1-xCuxO3（x=10%,14%,15%,16%,18%,20% have been prepared by sol-gel process. The temperature dependences of resistance and magnetoresistance （MR） of all the samples were measured from 77 K up to 350 K. From the results we can find that the whole series of the samples present the behavior of insulator in the whole temperature region measured rather than the transition of the phase from metal to insulator （M-I） . Using the function of lnρ-T^-（1/4） ,we fit the ρ-T curves of all the samples ,and find that the function of lnρ-T^-（1/4） of the samples with x=10% ,14% appear to be linear in the whole temperature region, and so do the samples with x=15% ,16%, 18% and 20% in the high temperature region. Basing on the MottOs VRH model,we make the explanation to this phenomena. From the experiment result it also can be shown that ,in the whole temperature region,the MR of all the samples appear to be tunneling MR. ,which well fit the tunneling MR model established by us using Monte Carlo simulated method.
出处
《稀土》
EI
CAS
CSCD
北大核心
2007年第3期22-25,共4页
Chinese Rare Earths
基金
福建省自然科学基金重点项目(E0320002)
