溶液旋涂法制备BixY3-xFe5O12薄膜的自旋输运特性

钇铁石榴石(yttrium iron garnet,YIG)的自旋输运特性一直是自旋电子学的研究重点之一.Bi作为YIG最常见的掺杂元素,其薄膜Bi_xY_3-xFe₅O₁₂的磁光特性已经被广泛研究.但Bi³⁺取代Y³⁺对YIG自旋输运的影响规律还没有被系统地研究过.本文利用溶液旋涂法制备了不同掺杂比的Bi_xY_3-xFe₅O₁₂薄膜,并研究Bi掺杂对YIG薄膜形貌结构和自旋输运性能的影响.结果表明Bi掺杂没有改变YIG的晶体结构,掺杂比上升令薄膜的吸收强度增大,带隙减小.XPS表明了Bi³⁺和Bi²⁺的存在.Bi掺杂在自旋输运上的调控体现在Bi_xY_3-xFe₅O₁₂薄膜的磁振子扩散长度相比纯YIG薄膜有所减小.同时研究发现Pt/Bi_x...     

模式识别预报双阳离子共交换Cu,Me-ZSM-5分子筛对NO分解的催化活性

本文采用模式识别方法,分析了用于NO分解反应的分子筛催化剂Cu,Me-ZSM-5中的第二种交换阳离子Me对其活性的影响.根据模式识别二维分类图,很好地预报了不同活性的催化剂.并初步讨论了引入共交换金属离子导致催化剂活性变化的原因.     

模式识别预报双氧离子共交换Cu,Me-ZSM-5分子筛对NO分解的催化活性

本文采用模式识别方法.分析了用于NO分解反应的分子筛催化剂Cu,Me-ZSM-5中的第二种交换阳离子Me对其活性的影响.根据模式识别二维分类图.很好地预报了不同活性的催化剂,并初步讨论了引入共交换金属离子导致催化剂活性变化的原因.     

Large positive magnetoresistance in photocarrier-doped potassium tantalites

We report on the high-field magnetotransport of KTaO₃ single crystals, which are a promising candidate for study in the extreme quantum limit. By photocarrier doping with 360 nm light, we observe a significant positive, non-saturating, and linear magnetoresistance at low temperatures accompanied by a decreasing Hall coefficient. When cooling down to 10 K, the magnetoresistance value of KTaO₃ (100) reaches ～ 433% at a magnetic field of 12 T. Such behavior can be attributed to all the electrons occupying only the lowest Landau level in the extreme quantum limit. Light inhomogeneity may also contribute to large linear magnetoresistance. These results provide insights into novel magnetic devices based on complex materials and add a new family of materials with positive magnetoresistance.     

人工神经网络-紫外光谱定量多组分体系的研究

本文系统地考察了人工神经网络(ANN)-紫外光谱(UVS)同时定量多组分混合溶液时参数选择对网络训练和预报性能的影响.合理选取诸参数,可提高训练效率改善预报性能,而且所优化的参数集可移植到其它相似体系。     

Anisotropic transport properties in the phase-separated La_(0.67)Ca_(0.33)MnO_3/NdGaO_3 (001) films

The anisotropic transport property was investigated in a phase separation La_(0.67)Ca_(0.33)MnO_3(LCMO) film grown on(001)-oriented Nd GaO_3(NGO) substrate. It was found that the resistivity along the b-axis is much higher than that along the a-axis. Two resistivity peaks were observed in the temperature dependent measurement along the b-axis, one located at 91 K and the other centered at 165 K. Moreover, we also studied the response of the resistivities along the two axes to various electric currents, magnetic fields, and light illuminations. The resistivities along the two axes are sensitive to the magnetic field. However, the electric current and light illumination can influence the resistivity along the b-axis obviously, but have little effect on the resistivity along the a-axis. Based on these results, we believe that an anisotropicstrain-controlled MnO_6 octahedra shear-mode deformation may provide a mechanism of conduction filaments paths along the a-axis, which leads to the anisotropic transport property.     

BaTiO_3/La_(0.67)Sr_(0.33)MnO_(3-δ)复合薄膜的磁致电极化和磁介电特性研究

采用脉冲激光沉积法制备了BaTiO_3(BTO)与缺氧的铁磁绝缘态La_(0.67)Sr_(0.33)MnO_(3-δ)(LSMO)构成的磁电复合薄膜,研究了20—300K温度区间内磁场对电极化特性和介电特性的影响.研究发现,施加磁场使得电滞回线的剩余极化强度和矫顽场均增大,其变化率峰值分别为111.9%和89.6%,峰值温度分别为40K和60K.异质结具有显著的磁介电效应,在测量温度区间内,磁场使得介电常数增大,介电损耗减小.在0.8T场强下,介电常数的最大磁致变化率出现在60K,达到了300%,而介电损耗也在此温度实现了最大变化,减小为零场时的50.9%.该磁电复合薄膜的磁致电极化和磁介电特性的极值均出现在LSMO层的磁电阻峰值温度附近,这说明磁场对电滞回线和介电参数的调制应该源自电荷相关的耦合作用.其可能的机理是磁场使得锰氧化物中的Mn离子局域磁矩趋于有序排列,并通过自旋-轨道耦合以及界面效应间接影响了BTO的电极化特性.研究结果对于多铁器件的开发和应用具有重要意义.