Microwave study of superconducting Sn films above and below percolation
Manfred H. Beutel, Nikolaj G. Ebensperger, Markus Thiemann, Gabriele Untereiner, Vincent Fritz, Mojtaba Javaheri, Jonathan Nägele, Roland Rösslhuber, Martin Dressel, Marc Scheffler
备注：
9 pages, 5 figures
发表信息：
Manfred H Beutel et al 2016 Supercond. Sci. Technol. 29 085011
The electronic properties of superconducting Sn films ($T_c \approx$ 3.8 K) change significantly when reducing the film thickness down to a few nm, in particular close to the percolation threshold. The low-energy electrodynamics of such Sn samples can be probed via microwave spectroscopy, e.g. with superconducting stripline resonators.
Here we study Sn thin films, deposited via thermal evaporation -ranging in thickness between 38 nm and 842 nm- which encompasses the percolation transition. We use superconducting Pb stripline resonators to probe the microwave response of these Sn films in a frequency range between 4 GHz and 20 GHz at temperatures from 7.2 K down to 1.5 K. The measured quality factor of the resonators decreases with rising temperature due to enhanced losses. As a function of the sample thickness we observe three regimes with significantly different properties: samples below percolation, i.e. ensembles of disconnected superconducting islands, exhibit dielectric properties with negligible losses, demonstrating that macroscopic current paths are required for appreciable dynamical conductivity of Sn at GHz frequencies. Thick Sn films, as the other limit, lead to low-loss resonances both above and below $T_c$ of Sn, as expected for bulk conductors. But in an intermediate thickness regime, just above percolation and with labyrinth-like morphology of the Sn, we observe a quite different behavior: the superconducting state has a microwave response similar to the thicker, completely covering films with low microwave losses; but the metallic state of these Sn films is so lossy that resonator operation is suppressed completely.
Magnetostrictive thin films for microwave spintronics
多铁性复合材料由耦合的铁磁相和压电相组成，在推动为信息和通信技术创造更快、更小和更节能的设备方面具有重要意义。这种器件需要具有大磁致伸缩和窄微波谐振线宽的薄铁磁膜。由于薄膜中的结构缺陷和界面效应，与体材料相比，这两种性能通常会降低。我们报告的发展单晶薄膜Galfenol（Fe 81 Ga 19）的磁致伸缩大的最佳报告值为散装材料。这使得磁各向异性和微波谐振频率被调谐的电压引起的应变，具有更大的磁电响应和更窄的线宽比任何以前报道的Galfenol薄膜。这些性质的组合使得单晶薄膜成为开发用于磁信息存储、处理和微波通信的可调谐器件的优秀候选材料。
Coupling of microwave magnetic dynamics in thin ferromagnetic films to stripline transducers in the geometry of the broadband stripline ferromagnetic resonance
Excitation and reception of magnetostatic surface spin waves in thin conducting ferromagnetic films by coplanar microwave antennas. Part II: Experiment
Measurement of the nonlinear Meissner effect in superconducting Nb films using a resonant microwave cavity: A probe of unconventional pairing symmetries
Absolute measurement of penetration depth of superconducting thin films using microwave stripline resonators
Tata Institute of Fundamental Research（塔塔基础研究所）；School of Physical Sciences, UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai（孟买大学物理科学学院，UM-DAE基础科学卓越中心）
Magnon Kerr Effect in a Magnetic Thin Film Strongly Coupled to a Microwave Resonator
ETH Zurich（苏黎世联邦理工学院）；Kyoto University（京都大学）；CNRS, Université de Bretagne Occidentale（法国国家科学研究中心，布列塔尼西部大学）；University of Konstanz（康斯坦茨大学）；Université Grenoble Alpes, CNRS, Institut Néel（格勒诺布尔阿尔卑斯大学，法国国家科学研究中心，内埃尔研究所）
Directional vortex pinning at microwave frequency in YBa$_{2}$Cu$_3$O$_{7-x}$ thin films with BaZrO$_3$ nanorods
研究了用脉冲激光烧蚀法从含5%（摩尔分数）BaZrO $_3$的靶上生长的YBaPDMATHABMM CuPDMATHABMN O $_{7-x}$薄膜的各向异性和定向钉扎效应. BaZrO $_3$夹杂物自组装得到沿c轴取向的纳米棒，从而为涡旋钉扎提供了优先方向。涡旋响应的方向性研究在高交流频率与复杂的微波响应在48 GHz，作为一个功能的应用领域和领域和c轴之间的角度$θ$。复杂的微波响应不表现出任何角度缩放，这表明YBa $_2$ Cu $_3$ O $_{7-x}$的结构各向异性的补充，至少另一个优选的取向。钉扎参数$r$显示定向钉扎的证据，在围绕c轴的宽范围的角度中有效（因此归因于BZO纳米柱）。
