中文摘要：

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，Gd^3＋掺杂后的样品（La0．975Gd0．025）4／3Sr5／3Mn2O7的三维磁有序转变温度（碟P）、磁化强度（M）均降低，这是由于Gd蚪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TC^3D〈T〈300K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TC1^3D（La4／3Sr5／3Mn2O7样品的三维磁有序转变温度，碟P）〈T〈300K温度范围内均以三维变程跳跃的方式导电，分析得出Gd^3＋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．

英文摘要：

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.