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首页> 外文会议>Symposium on Epitaxial Oxide Thin Films III March 31-April 2, 1997, San Francisco, California,U.S.A >New insights into the transport and field-enhancement effects in sol-gel derived colossal magnetoresistive thin films
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New insights into the transport and field-enhancement effects in sol-gel derived colossal magnetoresistive thin films

机译：溶胶凝胶衍生的巨大磁阻薄膜中的输运和场增强效应的新见解

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The transport mechanism underlying the colossal magnetoresistance (CMR) of doped manganites is not yet understood and their technological applications are limited by the high fields (approx 1T) required to obtain any significant MR. Following the development of a polymeric chemical synthesis route, we have investigated the O_2p unoccupied density of states in sol-gel derived La_1-xSr-xMnO_3 (0<=x<=0.7) thin films grown epitaxially on LaAlO_3, by electron energy-loss spectroscopy at sub-eV resolution. The spectra show a distinct prepeak in the OK edge at the Fermi level,the intensity of which correlates directly with the conductivity of the film. Similar correlation was also obtained for La_0.7Sr_0.3MnO_3-z annealed in vacuum to obtain well defined oxygen ocntent (z) in the film. this confirms that the charge carriers in these manganese perovskites have significant oxygen 2p hole character and suggests that the "double exchange" mechanism has to be modified. In another set of experiments we have studied room-temperature field amplification effect to enhance the low-field sensitivity of La_0.7Sr_0.3MnO_3-z films sandwiched between two thin rectangular slices of either alpha -Fe or Mn-Zn ferrite. This field amplification leads to an enhanced low-field MR value as high as 6
机译：掺杂锰铁矿的巨大磁阻（CMR）的传输机理尚未被了解，其技术应用受到获得任何重要MR所需的高磁场（约1T）的限制。随着聚合物化学合成路线的发展，我们研究了在LaAlO_3上外延生长的溶胶-凝胶衍生的La_1-xSr-xMnO_3（0 <= x <= 0.7）薄膜中O_2p的未占据状态密度，其电子能量损失低于eV分辨率的光谱。光谱在费米能级的OK边缘显示出明显的预峰，其强度与薄膜的电导率直接相关。对于在真空中退火的La_0.7Sr_0.3MnO_3-z也获得了相似的相关性，从而在膜中获得了明确定义的氧饱和度（z）。这证实了这些钙钛矿型锰中的载流子具有显着的氧2p空穴特征，并表明必须修改“双交换”机制。在另一组实验中，我们研究了室温场放大效应，以增强夹在两个薄的矩形α-Fe或Mn-Zn铁氧体矩形薄片之间的La_0.7Sr_0.3MnO_3-z薄膜的低场灵敏度。该场放大导致增强的低场MR值高达6

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