A位Eu掺杂对La_(0.7)Ca_(0.3)MnO_3电输运的影响  

EFFECT OF EU DOPING ON THE ELECTRICAL TRANSPORTATION PROPERTY OF La_(0.7)Ca_(0.3)MnO_3

作　　者：代国红[1] 皮厚礼[1] 熊永红[1] 任忠明[1] 张炯[1] 朱永丹[1] 熊曹水[1] 

机构地区：[1]华中科技大学物理系,武汉430074

出　　处：《低温物理学报》2006年第4期330-333,共4页Low Temperature Physical Letters

基　　金：国家自然科学基金(项目编号:10274022)资助的课题.~~

摘　　要：采用传统的固相反应法制备出了高质量的La_(0.7)Ca_(0.3)MnO_3(其中x=0.00,0.05,0.10,0.15,0.20)系列样品,并对其进行了XRD,电阻-温度测量.实验结果表明,随着Eu掺杂量的增加,样品的金属-绝缘体转变温度朝低温附近移动,峰值电阻增加.通过对A位平均离子半径和尺寸无序度的计算,我们发现,由Eu掺杂导致A位平均离子半径〈rA〉减小,尺寸无序度σ2增大,使晶格畸变加剧,从而削弱了eg巡游电子在Mn3+和Mn4+之间的跃迁,同时促进了自旋极化子的形成.我们还对样品电阻-温度曲线的高温部分进行了拟合,对于x=0.00的样品,曲线可以用非绝热近似下的小极化子模型拟合;当掺杂量为x=0.05,0.10,样品的导电机理符合变程跳跃模型;进一步加大掺杂量,当x=0.15,0.20时,样品的电输运行为可以用晶格极化子与自旋极化子共存来解释.We have fabricated high-quality polycrystalline samples of La0.7-xEu, Ca0.3MnO3 （x = 0. 00, 0. 05, 0. 10, 0.15, 0.20） using the conventional solid-state reaction method. Powder X-ray diffraction and the temperature dependence of resistance measurements are carried out to analyze the samples＇ properties. The experimental results indicate that with the increase of Eu dopant, MIT （ metal-insulator transition） temperature moves to lower temperature and the peak resistance become higher. We also calculate the average A-site ion radius （rA ） and size disorder 0.2 of all samples, respectively. From the calculated data, we obtain that, with the increase of Eu dopant, the reduced average A-site radius （rA ） and enlarged size disorder 0.2 lead to the suppression of the hopping of itinerant electron between Mn^3＋-O^2- - Mn^4＋ and aiding the formation of lattice polarons. We also fit the data with several physical models. As to x =0.00, nonadiabatic polaron is the best fitted model; As to x = 0.05,0.10, their R - T curves obey variable range hopping model very well, but with the increase of dopant, when x = 0. 15,0.20, the transportation mechanism could be explained by the coexistence of lattice and spin polarons.

关 键 词：金属-绝缘体转变 电阻-温度曲线 稀土金属掺杂 

分 类 号：O484.3[理学—固体物理]