为了澄清结构无序对电输运特性,特别是低温下电阻极小的影响,采用脉冲激光沉积方法在LalO3(100)基片上制备了两类La2/3Sr1/3MnO3薄膜.一块是在通40Pa氧气的气氛下沉积,沉积后不再进行通氧气的原位退火.另一块在同样通40Pa氧气的气氛下沉积,但沉积后再在6×104Pa的氧气气氛下进行原位退火.对两种薄膜的结构,磁特性和电输运特性进行了对比研究.结果表明:氧缺陷导致了薄膜结构的无序,更导致了类似自旋玻璃行为的磁无序.电输运特性结果表明原位退火使得薄膜的金属一绝缘体转变温度Tc从约195K提高到335K.对由于结构无序的存在对低温电阻较小行为的影响作了系统对比研究,曲线拟合的结果表明对于缺氧薄膜和进行了原位退火的薄膜的低温电阻较小行为的主要影响因素分别是类近藤散射作用和电子一电子相互作用,这一结果对于澄清庞磁电阻锰氧化物体系的低温电阻极小现象有一定积极意义.
In order to clarify the effect of structural disorder on electric transport, especially low-temperature re-sistance minimum, we grown the La2/3Sr1/3MnO3 thin films with various oxygen deficient on LaAlO3(100) sub-strates by pulsed laser deposition (PLD) technique. The oxygen-deficient film was deposited at very low oxygen pressure(40Pa) without post-growth annealing. Another normal film is also grown at a low oxygen pressure (40Pa), but has a post-growth annealing procedure (6 × 104 Pa). The structural, magnetic and electric properties are systemically studied. The results show that the oxygen deficiency causes in the lattice structural distortion, and further induces to more magnetic disorder with spin glass-like accompanying the structural disorder. The electric transport measurement shows that the M～I transition temperature Tc, increases from 195 K for without post-annea-ling sample to 335 K for with post-annealing sample about. The effect of structural disorder on low temperature re-sistance minimum behaviors was systemically studied. For both cases, without post-annealing and with post-annea-ling, the excellent fitting was given by considering Kondo-like spin dependent scattering, e-e interaction and related factors. The present results will be meaning to clarify the physical mechanism of low temperature resistance mini-mum in CMR manganites.
参考文献
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