Geometrical barriers and lower critical field in MgB2 single crystals

L. Lyard (1) , Thierry Klein (1, 2) , J. Marcus (1) , R. Brusetti (3) , C. Marcenat (4) , M. Konczykowski (5) , V. Mosser (6) , K.H. Kim (7) , B.W. Kang (7) , H.S. Lee (7) , S.I. Lee (7)

1 LEPES - Laboratoire d'Etudes des Propriétés Electroniques des Solides
2 IUF - Institut universitaire de France
3 CRTBT - Centre de Recherches sur les Très Basses Températures
4 SPSMS - UMR 9001 - Service de Physique Statistique, Magnétisme et Supraconductivité
5 LSI - Laboratoire des Solides Irradiés - Irradiated Solids Laboratory
6 ITRON
7 NVCRICS

The first penetration field sHpd has been deduced from local magnetization and specific heat measurements in magnesium diboride single crystals. For Ha ic, the geometrical barriers (GB) play a dominant role in the irreversibility mechanism. In thin samples, neglecting the GB in this direction would then lead to a large overestimation of Hc1 deduced from Hp through the standard elliptical formula. The lower critical field is found to be isotropic at low temperature (0.11±0.01 T).

Domaines: Supraconductivité [cond-mat.supr-con]

L. Lyard, Thierry Klein, J. Marcus, R. Brusetti, C. Marcenat, et al.. Geometrical barriers and lower critical field in MgB2 single crystals. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2004, 70, pp.180504(R). ⟨10.1103/PhysRevB.70.180504⟩. ⟨hal-00957726⟩