论文标题
从弱局部制度到ND_ {0.7} la_ {0.3} nio_ {3}胶片中的强大本地化制度的连续过渡
Continuous transition from weakly localized regime to strong localization regime in Nd_{0.7}La_{0.3}NiO_{3} films
论文作者
论文摘要
我们报告了金属绝缘体过渡（MIT）的研究，使用电导率和磁连导率（MC）测量nd_ {0.7} la_ {0.7} la_ {0.3} nio_ {3}胶片在laalo_ {3}（lao），srtio_ _ {3}的结晶底物上生长在胶片上。 Ndgao_ {3}（NGO）通过脉冲激光沉积。该薄膜在老挝生长的薄膜具有压缩菌株，并显示了金属行为，弱电阻率上升到2 K以下，这与弱定位贡献的发作有关。在Sto和非政府组织上生长的膜显示出从正温度系数（PTC）电阻状态到明确温度下的负温度系数（NTC）电阻状态的交叉。我们确定冷却时从PTC到NTC的交叉不一定构成MIT，因为零温度下的外推电导率σ_{0}尽管小（<10 s/cm）是有限的，但表明存在不良金属状态，并且没有激活的运输。与在Sto上生长的膜相比，在非政府组织上生长的电影的σ_{0}的值减少了40倍。我们表明，某些物理因素的结合使镍酸盐取代（已知会表现出一阶Mott型过渡），经历了连续过渡，如经历了无序/组成驱动的Anderson过渡的系统中所见。 MC测量还支持上述观察结果，并表明在低温下存在量子干扰引起的正mC，该量子干扰与自旋相关的负MC并存，随着电子在NGO上生长的膜中的强烈局部态度，该MC逐渐强大。
We report an investigation of Metal Insulator Transition (MIT) using conductivity and magnetoconductance (MC) measurements down to 0.3 K in Nd_{0.7}La_{0.3}NiO_{3} films grown on crystalline substrates of LaAlO_{3} (LAO), SrTiO_{3} (STO), and NdGaO_{3}(NGO) by pulsed laser deposition. The film grown on LAO experiences a compressive strain and shows metallic behavior with the onset of a weak resistivity upturn below 2 K which is linked to the onset of weak localization contribution. Films grown on STO and NGO show a crossover from a Positive Temperature Coefficient (PTC) resistance regime to Negative Temperature Coefficient (NTC) resistance regime at definite temperatures. We establish that a cross-over from PTC to NTC on cooling does not necessarily constitute a MIT because the extrapolated conductivity at zero temperature σ_{0} though small (<10 S/cm) is finite, signalling the existence of a bad metallic state and absence of an activated transport. The value of σ_{0} for films grown on NGO is reduced by a factor of 40 compared to that for films grown on STO. We show that a combination of certain physical factors makes substituted nickelate (that are known to exhibit first order Mott type transition), undergo a continuous transition as seen in systems undergoing disorder/composition driven Anderson transition. The MC measurement also support the above observation and show that at low temperature there exists a positive MC that arises from the quantum interference which co-exists with a spin-related negative MC that becomes progressively stronger as the electrons approach a strongly localized state in the film grown on NGO.
