Using microbridge technique, we have studied the vortex dynamics in a very low-temperature region ͑i.e., T / T c → 0͒ of the B-T phase diagram of Bi 2 Sr 2 Ca 1 Cu 2 O 8+␦ single crystal. We distinguish two types of vortex dynamics near the depinning threshold depending on the magnitude of the vortex-vortex interactions. For 0.01Յ 0 H Ͻ 1 T, we show that current-voltage ͑I-V͒ characteristics are strongly dependent on the history of magnetic field and current cycling. The sharp peak, so-called "peak effect," observed in 0 H-I c curve is due to a metastable state that can be removed after current cycling. At low field, I-V curves show steps that would be clearly related to "fingerprint phenomenon" since the relationship R d = dV / dI exists. This can be attributed to vortices flow through uncorrelated channels for the highly defective lattice. Indeed, as field sufficiently increases, these peaks merge to make broader ones indicating a crossover from filamentary strings to braid riverlike in which vortex-vortex interactions becomes significant. As confirmed by the discontinuity in the critical exponent value  determined in the vicinity of the threshold current using the power-law scaling V ϳ͑I − I c ͒  with a crossover from  = 2.2 to  = 1.2. The strong vortex correlation along the c axis has been clearly demonstrated using the dc-flux-transformer geometry for transport measurements that confirms the pseudo-two-dimensional ͑2D͒ behavior of the flux-line lattice. Our transport studies are in good agreement with simulations results of 2D elastic objects driven by repulsive interactions through a random pinning potential.
Through the employment of a novel approach in solving the dispersion for the three-layer plasmonic waveguides, considering lossy metals, we demonstrate that, besides well-known modes, the complete dispersion always contains high-lossy periodic solutions. Consideration of these solutions is shown to be crucial for the understanding of every aspect of dispersion evolution at broad spectral range when the thickness of the middle layer is varied. In particular, we show that generally considered modes of the three-layer waveguide transform into the single interface modes via interaction with high-lossy periodic solutions. Furthermore, the negative index mode is shown to experience a transition between low- and high-lossy regimes depending on the waveguide's thickness. Our results, avoiding complicated analytical analysis, perfectly integrate and importantly complement past theoretical works.
We conducted an experimental investigation of the structural and magnetic properties of Al-Mn-doped ZrO 2 and ZnO thin films. It was found that, even though additional Al doping does not substantially enhance ferromagnetism (FM), it influences surface magnetism by enhancing it. Increase of the Al concentration slightly improves the overall magnetization of the Al-Mn-doped ZrO 2 sample, however, this effect is also accompanied by a deterioration of the crystallinity of the sample. On the other hand, we found that by co-doping the Mn-doped ZnO samples with Al, the result is a significant increase of the magnetic moment. Apart from the surface effects, the data clearly indicate that the observed FM originates from defects. Our results confirm that co-doping with Al can be an efficient way to enhance magnetism and control the distribution of defects for certain transition-metal-doped semiconducting oxides.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.