Browsing by Author "Tamegai, T."

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Experimental Presentation of Microwave Absorption due to Shaking of JV by AC Magnetic Field in Bi2212 and Bi2223
(2009-05-01)
Shaltiel, D.
;
von Nidda, H. -A. Krug
;
Shapiro, B. Y.
;
Rosenstein, B.
;
Loidl, A.
The Josephson Vortex dynamics in high anisotropy superconductors Bi2212 and Bi2223 induced by AC magnetic field collinear to DC magnetic field and parallel to the layers is studied via their interaction with microwave field. Experimental results as function of DC magnetic field, AC magnetic field and temperature are presented. The AC induced microwave dissipation is larger than dissipation without AC field. The results are explained by the theoretical interpretation reported recently due to shaking by the AC field that depins the JV (Shaltiel et al., Phys. Rev. B 77, 014508, 2008). Similar behavior in these two compounds as a function of the variables involved discloses that the shaking effect should be observed in any high anisotropy superconductors. It shows that the AC field interacting with JV has an active and not the usual passive modulating role of the DC field in EPR dissipation experiments. The technique can be used to investigate JV dynamics and JV phase diagram.
Field cooling memory effect in Bi2212 and Bi2223 single crystals
(2010-07-01)
Shaltiel, D.
;
von Nidda, H-A Krug
;
Rosenstein, B.
;
Shapiro, B. Ya
;
Golosovsky, M.
A memory effect in the Josephson vortex system created by a magnetic field in the highly anisotropic superconductors Bi2212 and Bi2223 is demonstrated using microwave power absorption. This surprising effect appears despite a very low viscosity of Josephson vortices compared to Abrikosov vortices. The superconductor is field-cooled in a DC magnetic field H(m) oriented parallel to the CuO planes through the critical temperature T(c) down to 4 K, with subsequent reduction of the field to zero and again above H(m). A large microwave power absorption signal is observed at a magnetic field just above the cooling field, clearly indicating a memory effect. The dependence of the signal on a deviation of the magnetic field from H(m) is the same for a wide range of H(m) from 1500 to 17 000 G.
Interaction between Josephson and pancake vortices investigated by the induced microwave dissipation by ac magnetic field technique
(2008-06-01)
Shaltiel, D.
;
von Nidda, H. -A. Krug
;
Shapiro, B. Ya.
;
Rosenstein, B.
;
Loidl, A.
In the "induced microwave dissipation by ac magnetic field" (IMDACMF) technique, only the motion of Josephson vortices (JV) but not of pancake vortices (PV) induces microwave dissipation. This unique property is used to investigate the interaction between JV and PV in the high anisotropy superconductor Bi2212 as a function of magnetic field and tilting angle away from the a-b plane. In general, pinning of JV by PV inhibits the motion of the JV and, thus, reduces the microwave dissipation. Almost no pinning of JV is obtained at low dc magnetic fields even at high-tilting angles. Strong pinning of JV due to their interaction with PV is observed at higher magnetic fields and at tilting angles between 50 degrees and 90 degrees. The technique enables to observe transitions from the JV state to the crossing lattice state, without and with interaction between JV and PV, and to the one-dimensional vortex chains. The results obtained by the present technique are compared to results of surface imaging techniques, which investigate the interaction between PV and JV probing the PV.
Interplay of anisotropy and disorder in the doping-dependent melting and glass transitions of vortices in Bi2Sr2CaCu2O8+delta
(2007-04-20)
Beidenkopf, H.
;
Verdene, T.
;
Myasoedov, Y.
;
Shtrikman, H.
;
Zeldov, E.
We study the oxygen doping dependence of the equilibrium first-order melting and second-order glass transitions of vortices in Bi2Sr2CaCu2O8+delta. Doping affects both anisotropy and disorder. Anisotropy scaling is shown to collapse the melting lines only where thermal fluctuations are dominant. Yet, in the region where disorder breaks that scaling, the glass lines are still collapsed. A quantitative fit to melting and replica symmetry-breaking lines of a 2D Ginzburg-Landau model further reveals that disorder amplitude weakens with doping, but to a lesser degree than thermal fluctuations, enhancing the relative role of disorder.
On investigation of high T(c) superconductors with Electron Paramagnetic Resonance spectrometers
(2010-11-15)
Shaltiel, D.
;
von Nidda, H. -A. Krug
;
Shapiro, B. Ya.
;
Bogoslavsky, B.
;
Rosenstein, B.
Following the discovery of high T(c) superconductors, many researchers have applied EPR spectrometers to investigate their properties using the regular instructions to operate the spectrometer. As no substantial information was obtained it was soon practically abandoned. Investigations performed recently with the EPR technique, using a different operating method than the conventional one and the introduction of a detailed theoretical study related to the interaction of the JV with the microwave magnetic field lead to new and important results related to properties of high anisotropy superconductors indicating that the EPR spectrometer can be used to investigate properties of high anisotropy superconductors. The failures when using conventional operating method to obtain meaningful results and the method used in the present work to carry out the measurements in a proper manner are presented. Some important results obtained in investigating high anisotropy superconductors by the EPR technique are presented. (C) 2010 Elsevier B.V. All rights reserved.
On investigation of high T-c superconductors with Electron Paramagnetic Resonance spectrometers
(2010-11-15)
Shaltiel, D.
;
von Nidda, H. -A. Krug
;
Shapiro, B. Ya.
;
Bogoslavsky, B.
;
Rosenstein, B.
Following the discovery of high T-c superconductors, many researchers have applied EPR spectrometers to investigate their properties using the regular instructions to operate the spectrometer. As no substantial information was obtained it was soon practically abandoned. Investigations performed recently with the EPR technique, using a different operating method than the conventional one and the introduction of a detailed theoretical study related to the interaction of the JV with the microwave magnetic field lead to new and important results related to properties of high anisotropy superconductors indicating that the EPR spectrometer can be used to investigate properties of high anisotropy superconductors. The failures when using conventional operating method to obtain meaningful results and the method used in the present work to carry out the measurements in a proper manner are presented. Some important results obtained in investigating high anisotropy superconductors by the EPR technique are presented. (C) 2010 Elsevier B.V. All rights reserved.