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Electronic anisotropy, magnetic field-temperature phase diagram and their dependence on resistivity in c -axis oriented MgB 2 thin films

2001; IOP Publishing; Volume: 14; Issue: 6 Linguagem: Inglês

10.1088/0953-2048/14/6/304

1361-6668

S. Patnaik, L. D. Cooley, A. Gurevich, A. A. Polyanskii, Jianyi Jiang, X. Y. Cai, A.A. Squitieri, M.T. Naus, Min‐Ku Lee, Jae-Hyuk Choi, L. J. Belenky, Sang Don Bu, J Letteri, Xueyan Song, Darrell G. Schlom, S.E. Babcock, Chang‐Beom Eom, E. E. Hellstrom, D. C. Larbalestier,

Iron-based superconductors research

An important predicted, but so far uncharacterized, property of the new superconductor MgB2 is electronic anisotropy arising from its layered crystal structure. Here we report on three c-axis oriented thin films, showing that the upper critical field anisotropy ratio Hc2par/Hc2perp is 1.8 to 2.0, the ratio increasing with higher resistivity. Measurements of the magnetic field-temperature phase diagram show that flux pinning disappears at H* ~ 0.8Hc2perp(T) in untextured samples. Hc2par(0) is strongly enhanced by alloying to 39 T for the highest resistivity film, more than twice that seen in bulk samples.