Palavras-chave:
Magnetization, Irreversibility Line, High Critical Temperature Superconductors, Method solid state reactionResumo
The irreversibility properties of High-Tc superconductors are of major importance for technological applications. For example, a high irreversibility magnetic field is a more desirable quality for a superconductor (Viera, et al., 2001). The irreversibility line in the H-T plane is constituted by experimental points, which divides the irreversible and reversible behavior of the magnetization. The irreversibility lines for series of Lu1Gd2Ba5Cu8O18 and Lu 1.5 Gd Ba Cu O polycrystalline samples with different doping were investi- 1.5 5 8 18 gated. The samples were synthesized using the usual solid estate reaction method. Curves of magnetization ZFC (Zero Field Cooled) FC (Field Cooled) for the system Lu Gd Ba Cu O and Lu Gd Ba Cu O , were measured in 1 2 5 8 18 1.5 1.5 5 8 18 magnetic fields of the 100 to 2,000 Oe, and allowed to obtain the values for the irreversibility and critical temperatures. The data of irreversibility temperature allowed demarcating the irreversibility line, T H). Two main lines are used for irr(the interpretation of the irreversibility line: one of those which suppose that the vortexes are activated thermally and the other proposes that associated to Tirr
(Irreversibility Temperature) a phase transition occurs. The irreversibility line is described by a power law. The obtained results allow concluding that in the system Lu Gd Ba Cu O and Lu Gd Ba Cu O a characteristic bend of the 1 2 5 8 18 1.5 1.5 5 8 18 Almeida-Thouless (AT) tendency is dominant for low fields and a Gabay- Toulouse (GT) behavior for high magnetic fields.
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ANDERSON, P. S., KIRK, C.A., SKAKLE, J. M. S. & WEST, A. R. 2003. Synthesis and characterization of La BaCu O AND La BaCu MxO : 4 5 13+δ 4 5−x 13+δ M=Fe, Co, Ni, Zn J. Solid State Chem. 170 (1).
ANDERSON, P. W. & KIM, Y. B. 1964. Hard Superconductivity: Theory of the Motion of Abrikosov Flux Lines Review of Modern Physics, (New York) 36 (1)39.
BARDEN, J & STEPHEN, M. J. 1965 Theory of the Motion of Vortices in Superconductors. Phys. Rev.1197.
BARROS, F. M., VIEIRA, V.N. et al. 2004. Magnetoresistivity, fluctuation conductivity and magnetic irreversibility in the Y0.95Pr Ba Cu O7 com- 0.05 2 3 −δ pound: a case of split pairing transition physical C 408410 (632).
DAVOR-PAVUNA, M. C. 1992. Introduction to Superconductivity and High-Tc Materials, World Scienti_c Publishing Co. Pte. Ltd.
DE ALMEIDA, J. R. L. & THOULESS, D. J. 1978. Stability of the Sherrington-Kirkpatrick solution of a spin glass model. J. Phys. A 11 (983).
FISCHER, M.P.A. 1989. Vortex-glass superconductivity: A possible new phase in bulk high-Tc oxides Phys. Rev. Lett. 62 (1415).
GABAY, M. & TOULOUSE, G. 1981. Coexistence of Spin-Glass and Ferromagnetic Orderings Phys. Rev. Lett. 47 (201).
LANDINEZ-TELLEZ, D. A., ROA-ROJAS, J., MARTINEZ BUITRAGO, D. & PARRA VARGAS, C. A. 2008. Producción y caracterización del material superconductor Yb Sm Ba Cu O . Rev.Colomb. Fis. 40(1), 101. 103. 0.6 0.4 2 3 7
LARSON, A. C. & VON DREELE, R. B. 2000. General Structure Analysis System, Los Alamos National Laboratory Report LAUR, 86.
PENG, J. L., KLAVINS, P. et al. 1989. Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange Phys. Rev. B 39 (9074).
PARRA-VARGAS, C. A., LANDNEZ TELLEZ, D. A. & ROA-ROJAS, J. 2007. Determining superconducting parameters from analysis of magnetization fluctuation for CaLaBaCu O superconductor physical B 398 (301). 3 7−Δ
PARRA-VARGAS, C. A., PIMENTEL J. R., PUREUR, P., LANDINEZ TELLEZ, D. A. & ROA-ROJAS, J. 2009. Magnetization fluctuation analysis and superconducting parameters of La RE BaCaCu3O -δ(RE=Y, Sm, Gd, Dy, Ho, Yb) 0.5 0.5 7 superconductor physical B 404 (2766).
ROA-ROJAS, J, MENEGOTTO COSTA, R, PUREUR, P. & PRIETO, P. Fluctuaciones en la magnetoconductividad de bajo campo en superconductores texturizados de YBa Cu O7-Δ2000. Phys. Rev. B 61. 12457. 2 3
SKAKLE, J. M. S. & WEST, A. R. 1994. Superconducting La1 Ba y .5−x 1.5+x−CayCu Oz solid solutions I. Phase diagram, cation stoichiometry and Tc data 3 Physica C 220 (187).
TAVANA, A. & AKHAVAN, M. 2010. How Tc can go above 100 K in the YBCO family. Eur. Phys. J. B. 73, 7983.
TOBY, B. H. 2001. EXPGUI, a graphical user interface for GSAS. J. Appl. Crystallogr. 34, 210213
TOPAL, U. & AKDOGAN, M. 2011. Further increase of Tc in YBaCuO superconductors. J. Supercond. Nov. Magn. Doi:10.1007/s109480111129-1
UDOMSAMUTHIRUN, P., KRUAEHONG, T., NILKAMJON, T. & RATRENG, S. 2010. The new superconductors of YBaCuO materials. J. Supercond. Nov. Magn. 23, 13771380.
VIERIA, V.N & PUREUR, P.J. the effects of Sr and Ca on the magnetic irreversibility and fluctuation conductivity of ybco-123 2001. Schaf, Physics C 353-241.
YAGI, T., DOMON, M., OKAJIMA, Y. & YAMAYA, K. 1991. Low-temperature crystal structure and superconductivity in La BaxCuO Physica C 173. 453.
