Vortex Lattice in Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} Well Above the First-Order Phase-Transition Boundary

Measurements of non-local in-plane resistance originating from transverse vortex-vortex correlations have been performed on a Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} high-T_c superconductor in a magnetic field up to 9 T applied along the crystal c-axis. Our results demonstrate that a rigid vortex lattice does exist over a broad portion of the magnetic field -- temperature (H-T) phase diagram, well above the first-order transition boundary H_{FOT}(T). The results also provide evidence for the vortex lattice melting and vortex liquid decoupling phase transitions, occurring above the H_{FOT}(T).Comment: 14 pages, 10 figure

Evidence for internal field in graphite: A conduction electron spin resonance study

We report conduction electron spin resonance measurements performed on highly oriented pyrolitic graphite samples between 10 K and 300 K using S (f = 4 GHz), X (f = 9.4 GHz), and Q (f = 34.4 GHz) microwave bands for the external dc-magnetic field applied parallel (H || c) and perpendicular (H perp c) to the sample hexagonal c-axis. The results obtained in the H || c geometry are interpreted in terms of the presence of an effective internal ferromagnetic-like field Heff-int(T,H) that increases as the temperature decreases and the applied dc-magnetic field increases. We associate the occurrence of the Heff-int(T,H) with the field-induced metal-insulator transition in graphite and discuss its origin in the light of relevant theoretical models.Comment: 10 pages (tex), 5 figures (ps

High-temperature Local Superconductivity In Graphite And Graphite-sulfur Composites

Recently, the existence of localized superconducting domains at elevated temperatures has been demonstrated for both pure graphite and graphite-sulfur composites. In this note we report results of magnetization and magnetoresistance measurements which provide a further evidence for the local high-temperature superconductivity occurrence in these materials. © 2004 Elsevier B.V. All rights reserved.408-4101-47778Tanigaki, K., (1991) Nature, 352, p. 222Tang, Z.K., (2001) Science, 292, p. 2462Kopelevich, Y., (2000) J. Low Temp. Phys., 119, p. 691Kempa, H., (2002) Phys. Rev. B, 65, pp. 241101RKopelevich, Y., (2003) Phys. Rev. Lett., 90, p. 156402Das, D., Doniach, S., (2001) Phys. Rev. B, 64, p. 134511Feigel'man, M.V., (2001) Phys. Rev. Lett., 86, p. 1869Spivak, B., (2001) Phys. Rev. B, 64, p. 132502Ovchinnikov, Yu.N., (2001) Phys. Rev. B, 63, p. 064524Abrikosov, A.A., (2001) Phys. Rev. B, 63, p. 134518Da Silva, R.R., (2001) Phys. Rev. Lett., 87, p. 147001Yang, H.P., (2001) Chin. Phys. Lett., 18, p. 1648Moehlecke, S., (2002) Philos. Mag. B, 82, p. 1335González, J., (2001) Phys. Rev. B, 63, p. 13442