Co替代Mn的La_(0.4)Ca_(0.6)Mn_(1-x)Co_xO_3的磁电性质及电荷有序相  

Magnetic Properties and Charge Ordering Phase of La_(0.4)Ca_(0.6)Mn_(1- x)Co_xO_3 System by Co Substitution for Mn

作　　者：王桂英[1,2] 刘鹏[1,2] 李莉[1,2] 叶吾梅[1,2] 刘宁[3] 彭振生[1] 

机构地区：[1]宿州学院自旋电子与纳米材料安徽省重点实验室,安徽宿州234000 [2]宿州学院机械与电子工程学院,安徽宿州234000 [3]安徽科技学院理学院,安徽凤阳233100

出　　处：《稀有金属》2015年第5期421-427,共7页Chinese Journal of Rare Metals

基　　金：国家自然科学基金重点项目(19934003);安徽省自然科学基金项目(1308085MA11);安徽省教育厅自然科学研究重点项目(KJ2011A259;KJ2012Z404);宿州学院科研平台开放课题(2014YKF49;2012YKF07;2014YKF48)资助

摘　　要：用固相反应法制备La0.4Ca0.6Mn1-xCoxO3(x=0.02,0.04,0.06,0.08,0.10,0.12)系列样品,用X射线衍射(XRD)探测样品的结构,通过电阻率-温度(ρ-T)曲线、磁化强度-温度(M-T)曲线、电子自旋共振(ESR)谱,研究Co替代Mn对La0.4Ca0.6Mn O3磁电性质及电荷有序相的影响。结果表明:XRD图谱显示所有样品均形成良好的单相,没有任何杂相出现,说明Co已经进入Mn位并结晶良好;随Co替代量的增大,电阻率逐渐减小;随Co替代量的增大,反铁磁性减弱,铁磁性增强;x=0.02的样品,电荷有序相已基本融化,还有一些电荷有序相的残留,x=0.06的样品,电荷有序相完全融化。物理机制是,Co3+的电子结构是3d6,符合Oh对称,它不是Jahn-Teller(JT)离子,因为Co3+不是JT离子,所以Co3+替代Mn3+抑制了JT畸变。JT畸变减弱引起的影响:一方面使Mn3+—O2-—Mn4+键长缩短,键角增大,有利于双交换;另一方面,Mn3+的两个eg轨道劈裂产生带隙,Co3+替代Mn3+使带隙减小,提高了材料的导电性,使体系反铁磁性减弱铁磁性增强,从而破坏电荷有序相。A series of Lao.4Cao.6Mn1-xCoxO3 （x =0.02, 0.04, 0.06, 0.08, 0.10, 0.12） samples were prepared using solid-state reaction method. The structure of the samples was analyzed by X ray diffraction （ XRD）, and the effects of Co substitution for Mn on the magnetic properties and charge ordering of Lao.4 Ca0.6 MnO3 were studied by the measurements of magnetization-temperature （M-T） curves, resistivity-temperature （p-T） curve, electron spin-resonance （ESR） spectroscopy. The XRD patterns showed that all the sam- ples were good single-phase, which indicated that Co entered into the site of Mn and formed good crystals. With the increase of doping Co, the resistivity and antiferromagnetism decreased, and the ferromagnetism increased. When x was 0.02, the charge ordering phase was almost melted. However, the charge ordering phase was melted completely with x = 0.06. The electronic structure of Co3＋ was 3d6 and Oh symmetrical, reducing the distortion of Jahn-Teller （JT）. The decreased distortion of JT produced two influences： （1） the bond length of Mn3 ＋ -O2- -Mn4＋ shortened, and the bond angle increased, which favored a double exchange; （2） a band gap was formed between two es orbits of Mn3＋. However, the gap decreased with the Co3＋ substitution for Mn3＋ , which could improve the con- ductivity and increased the ferromagnetism, leading to a destruction of charge ordered phase.

关 键 词：Co替代Mn 电输运性质 磁性质 电荷有序 JAHN-TELLER畸变 

分 类 号：O482.54[一般工业技术—材料科学与工程] TM273[理学—固体物理]