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Sr3 Ti2 O7型四方结构,空间群为I 4/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(T 3DC1)、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T 3DC < 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T 3DC1(La4/3Sr5/3Mn2O7样品的三维磁有序转变温度, T 3DC0)< 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.
Abstract:
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 Gd3+ doping reduces the magnetic transition temperature (T3DC ) and magnetization (M) of the doped sample (La0.975Gd0.025)4/3Sr5/3Mn2O7, which is because Gd3+ 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 T 3DC < T <300 K, and therefore phase-separations occur. Electrical transportation measurements show that the electronic conducting mechanism in the temperature range of T 3DC
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