标题: 超薄La(0.7)Sr(0.3)MnO(3) / La(0.5)Ca(0.5)MnO(3)双层异质结构磁电特性研究
Magneto-transport properties of ultrathin La(0.7)Sr(0.3)MnO(3) / La(0.5)Ca(0.5)MnO(3) heterostructures
作者: 江尧薇
Chiang, Yao-Wei
庄振益
电子物理系所
关键字: 镧钙锰氧;镧锶锰氧;双层异质结构;庞磁阻材料;La(0.7)Sr(0.3)MnO(3);La(0.5)Ca(0.5)MnO(3);heterostructures;colossal magnetoresistance
公开日期: 2011
摘要: 钙钛矿锰氧化物被证实由于电荷、自旋、轨道及晶格自由度的强关联性而存在着丰富的物理特性,其中,La(0.5)Ca(0.5)MnO(3)具有CE-type反铁磁及电荷有序现象。另一方面,La(0.7)Sr(0.3)MnO(3)在居礼温度Tc = 380 K以下具有铁磁金属态,说明在此强关联系统,只要些微改变掺杂的物质,可能使磁电特性上有着非常不同的现象。在本文实验中利用脉冲雷射沉积法,分别制作不同厚度的单层La(0.5)Ca(0.5)MnO(3)与La(0.7)Sr(0.3)MnO(3)薄膜及La(0.7)Sr(0.3)MnO(3)(x nm) / La(0.5)Ca(0.5)MnO(3)(30 nm) / SrLaAlO(4)(001) ( x = 1.5、3、4.5、6、7.5)的双层结构,研究薄膜不同厚度及双层异质结构的磁电特性及之间可能的交互作用。
应变形态的不同可能影响La(0.7)Sr(0.3)MnO(3)薄膜的磁力线分布及磁异向性,因此,初步利用磁力显微镜(MFM)观察发现,单层La(0.7)Sr(0.3)MnO(3)薄膜在外加磁场下及成长在La(0.5)Ca(0.5)MnO(3)上的双层异质结构的磁力线分布皆会有所改变。比较单层个别薄膜与数种厚度的双层异质结构之磁电特性,发现皆有相变转变及特性的改变,本文将对造成改变的可能原因进行讨论。
Perovskite manganites have been demonstrated to exhibit rich emergent physics owing to the strong correlations among the charge, spin, orbital, and lattice degrees of freedoms. Among them, La(0.5)Ca(0.5)MnO(3) has been found to have the CE-type antiferromagnetic and charge ordering transition, simultaneously. On the other hand, the La(0.7)Sr(0.3)MnO(3) exhibits the ferromagnetic metallic phase below Tc 侧 380 K, indicating that merely slight changes in doping compositions may lead to drastic effects on the magneto-transport properties of these strongly-correlated systems.
In this work, single-layered La(0.5)Ca(0.5)MnO(3) and La(0.7)Sr(0.3)MnO(3) thin films with different thicknesses, as well as bilayered structure of La(0.7)Sr(0.3)MnO(3)(x nm) / La(0.5)Ca(0.5)MnO(3)(30 nm) / SrLaAlO(4)(001) (with x = 1.5, 3, 4.5, 6, 7.5) films were synthesized by the pulsed-laser deposition to investigate the effects of film thickness and possible interactions between the two different materials on magneto-transport properties of respective structures. We found that the magnetic anisotropy may be significantly modified by the type of strain imposed on the films. For instance, the preliminary magnetic force microscopy (MFM) study has shown that the magnetic line of force on the La(0.7)Sr(0.3)MnO(3) monolayer can be dramatically modified by the applied external magnetic field as well as by the underlying layer in the bilayered heterostructures. Systematic comparisons between the magneto-transport properties of single-layered films and that of the bilayered structures with comparable thicknesses were made and the underlying mechanisms giving rise to the observed results will be discussed.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079921518
http://hdl.handle.net/11536/49714
显示于类别:Thesis


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