Double Layered Thin Film Fabrication of a/c-controlled YBCO and Manganites, and Tunable Microwave Filters

双层铁磁/高温超导(HTS)可用于移动电话系统基站的可调谐微波滤波器。利用磁场改变铁层的磁导率，从而改变高温超导层上的微波传播。有必要获得完成这些功能的单层和双层。此外，阐明高温超导薄膜在磁场(H)作用下的微波吸收(MA)、双层沉积下的劣化问题以及薄膜在应用期间的逝去退化问题是非常重要的。在本项目中，我们研究了[1]铁基LSMO和-LBMO单层薄膜的生长，[2]LSMO/YBCO和LBMO/YBCO(YBCO：HTS层)双层薄膜的生长及其降解，[3]高温超导-YBCO和超晶格在磁场作用下的微波吸收。我们成功地在超低温…下种植了它们使用次数更多，获得了非常光滑的薄膜。我们可以完全控制a/c取向的生长，并阐明了a/c取向的表面迁移和迁移机制。LSMO和LBMO薄膜可以在超低温下生长。LSMO表现为二维阶梯生长模式。在a-YBCO底层上可以生长LSMO薄膜，但部分a-YBCO转变为c-YBCO。在LBMO底层上可以生长出高质量的YBCO外延层。在双层沉积过程中，Under-LBMO的结晶度没有下降，但双层表面变得更加粗糙。当LBMO沉积在YBCO层上时，表面非常光滑，而Under-YBCO在双层沉积过程中被降解。A-YBCO/Mg0的结晶度在几年内有较大的降解，而a-YBCO/LAO的结晶度没有明显的变化。用PLD法制备了高T_c(86K)a-YBCO和c-YBCO，并在高压下研究了它们的MA，发现c-YBCO的MA大于a-YBCO。H//a的MA比H//c的小，说明a-YBCO更适用于双层可调谐微波滤光片。理论分析表明，过屏电流机制是引起MA的主要因素。我们在LCMO/YBCO超晶格上测量了MA，发现了一个非常重要的事实，即垂直于平面的H的MA很大，而平行于平面的H的MA可以忽略不计。因此，当铁氧体/高温超导双层(超晶格)在不久的将来被用于可调谐微波滤光片时，我们可以提出在平行磁场下可以最小化高温超导层中的微波吸收。较少

Double layers of Ferromagnetic/Hi-Tc-Superconductors (HTS) can be used for tunable microwave filters at base stations of mobile phone system. Permeability of Ferro-layer is modified by magnetic field, leading to modification of microwave propagation on HTS-layer. It is necessary to obtain single-layers and double-layers which complete such functions. Further, it is important to elucidate microwave absorption (MA) in HTS under magnetic field (H), problems of deteriorations under the double layers depositions and elapsed-degradations of thin films in application periods. In this project, we studied [1] thin film growths of Ferro-LSMO and-LBMO single layers, [2] double layer depositions of LSMO/YBCO and LBMO/YBCO (YBCO: HTS-layer), and their degradations, [3] microwave absorptions in HTS-YBCO and Superlattices under magnetic field.YBCO thin films were deposited on Mg0 and LAO substrates by Ion Beam Sputtering (IBS) with oxygen plasma supply. We succeeded to grow them at ultra-low temperat … More ures and obtained extremely smooth films. We could control a/c-orientation growths completely and elucidated a mechanism of a/c-orientations <surface migration>. Fine crystalline LSMO and LBMO thin films could be grown at ultra-low temperatures. LSMO showed 2D step-terrace growth mode. LSMO over-layers could be grown on a-YBCO under-layers but a part of a-YBCO was changed into c-YBCO. High quality YBCO over-layers could be grown on LBMO under-layers. During the double-layer depositions, the crystallinity of under-LBMO was not degraded but the double-layer surface was much roughened. The surface was very smooth when LBMO was deposited on YBCO layers but under-YBCO was degraded during the double-layer depositions. The crystallinity showed large elapsed-degradations for a few years for a-YBCO/Mg0 but not for a-YBCO/LAO. It was known that the degradation is concerned with lattice matching.High Tc (86 K) a-YBCO and c-YBCO were fabricated by PLD, and their MA was investigated under H. MA was larger for c-YBCO than for a-YBCO. MA was smaller for H//a than for H//c then it was clarified that a-YBCO is more useful for the double-layered tunable microwave filters. It was elucidated by theoretical analysis that an <excess screening current mechanism> is a major factor for MA. We measured MA on LCMO/YBCO superlattice, and found a quite important fact that MA is large for H perpendicular to the plane but negligible small for H parallel to the plane. Thus we could propose that we can minimize the microwave absorption in HTS-layers for the parallel magnetic field when the Ferro/HTS double-layers (superlattices) will be used for tunable microwave filters in the near future. Less