钙钛矿锰氧化物(La_(1-x)Gd_x)_(4/3)Sr_(5/3)Mn_2O_7(x=0,0.025)磁性和输运性质研究  

Magnetic and transport properties of perovskite manganites (La_(1-x)Gd_x)_(4/3)Sr_(5/3)Mn_2O_7(x=0,0.025) polycrystalline samples

作　　者：王志国[1] 向俊尤 徐宝[1] 万素磊 鲁毅[1] 张雪峰[2] 赵建军[1] 

机构地区：[1]包头师范学院物理科学与技术学院,磁学与磁性材料重点实验室,包头014030 [2]内蒙古科技大学,内蒙古自治区白云鄂博矿多金属资源综合利用重点实验室,包头014010

出　　处：《物理学报》2015年第6期351-356,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11164019;11064008);包头科学技术局产学研合作项目(批准号:2014X1014-01)资助的课题~~

摘　　要：采用传统的高温固相烧结法制备了双层钙钛矿锰氧化物(La1-xGdx)4/3Sr5/3Mn2O7(x=0,0.025)多晶样品.通过X射线衍射仪研究发现样品为Sr3Ti2O7型四方结构,空间群为I4/mmm;磁性测量表明,Gd3+掺杂后的样品(La0.975Gd0.025)4/3Sr5/3Mn2O7的三维磁有序转变温度(T3D C1)、磁化强度(M)均降低,这是由于Gd3+的掺杂引起晶格的畸变,从而使得晶格常数发生改变,减弱了铁磁耦合而导致的;通过电子自旋共振谱测量发现,在T3D C<T<300 K温度范围内,两样品在顺磁的基体上均有短程的铁磁团簇存在,出现了相分离现象.电性测量表明:两样品分别在T3D C1(La4/3Sr5/3Mn2O7样品的三维磁有序转变温度,T3D C0)<T<300 K温度范围内均以三维变程跳跃的方式导电,分析得出Gd3+的掺杂使得载流子局域长度的减小.这表明载流子需要吸收更多的能量才能克服晶格的束缚进行跳跃,因此(La0.975Gd0.025)4/3Sr5/3Mn2O7样品的电阻较高.The polycrystalline samples of two-layered perovskite manganites （La1-xGdx）4/3Sr5/3Mn2O7（x=0,0.025） are prepared by traditional solid state reaction method. X-ray diffraction measurements show that both samples are of the Sr3Ti2O7-type tetragonal phase （space groups I4/mmm）. Magnetic measurements show that Gd^3＋ doping reduces the magnetic transition temperature （TC^3D） and magnetization （M） of the doped sample （La0.975Gd0.025）4/3Srs/3Mn2O7, which is because Gd^3＋ doping induces lattice distortion and change the lattice constant, and subsequently weakens the double exchange interactions. It is found from electron spin resonance measurements that short-range ferromagnetic clusters appear in the paramagnetic background of both samples at temperatures TC^3D 〈 T 〈300 K, and therefore phase-separations occur. Electrical transportation measurements show that the electronic conducting mechanism in the temperature range of TC^3D 〈 T 〈 300 K is in accordance with three-dimensional variable-range hopping. It is found that the sample （La0.975Gd0.025）4/3Sr5/3Mn2O7 has a higher resistance. This is because Gd^3＋ doping reduces the localization length of carriers, and makes conducting carriers absorb more energy to overcome the bound potentials in the lattice.

关 键 词：钙钛矿锰氧化物 相分离 双交换作用 

分 类 号：O482.5[理学—固体物理]