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

双层铁磁/高通量超导体（HTS）可用于移动电话系统基站的可调谐微波滤波器。磁场改变了铁层的磁导率，从而改变了微波在高温超导层上的传播。有必要获得完成这些功能的单层和双层。此外，阐明高温超导中磁场(H)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延时劣化问题也很重要。在本课题中，我们研究了铁-LSMO和LBMO单层[1]薄膜的生长，LSMO/YBCO和LBMO/YBCO （YBCO: hts层）双层[2]沉积，以及它们在HTS-YBCO和超晶格中的降解、[3]在磁场下的微波吸收。采用离子束溅射（IBS）技术在Mg0和LAO衬底上制备了YBCO薄膜。我们成功地在超低温下培养了它们，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a/c取向<地表迁移>的机制。LSMO和LBMO薄膜可以在超低温条件下生长。LSMO表现为二维阶梯阶地生长模式。LSMO层可以在a- ybco下层生长，但部分a- ybco变成了c-YBCO。在LBMO下层上可以生长出高质量的YBCO层。在双层沉积过程中，lbmo的结晶度没有降低，但双层表面明显粗糙化。在YBCO层上沉积LBMO时，表面非常光滑，但在双层沉积过程中，YBCO层下的表面降解。a- ybco /Mg0的结晶度在几年内有较大的下降，而a- ybco /LAO的结晶度没有下降。已知退化与晶格匹配有关。用PLD法制备了高Tc （86 K）的a-YBCO和c-YBCO，并在h下研究了它们的MA，其中c-YBCO的MA大于a-YBCO。H//a的MA比H//c的MA小，说明a- ybco对双层可调谐微波滤波器更有用。理论分析表明，<过筛电流机制>是MA发生的主要因素。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很小。因此，我们可以提出，在不久的将来，当铁/高温超导双层（超晶格）用于可调谐微波滤波器时，我们可以最大限度地减少平行磁场下高温超导层的微波吸收。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