Anisotropies of the Lower and Upper Critical Fields in MgB2 Single Crystals

L. Lyard (1) , P. Szabo (1, 2) , Thierry Klein (1, 3) , J. Marcus (1) , C. Marcenat (4) , K. H. Kim (5) , B.W. Kang (6) , H. S. Lee (5) , S. I. Lee (6)

1 LEPES - Laboratoire d'Etudes des Propriétés Electroniques des Solides
2 CLTP IEP - Centre of Low Temperature Physics
3 IUF - Institut universitaire de France
4 SPSMS - UMR 9001 - Service de Physique Statistique, Magnétisme et Supraconductivité
5 NVCRICS
6 NVCRICS

The temperature dependence of the upper (Hc2) and lower (Hc1) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions.We show that Hc2 Hc2kab=Hc2kc and Hc1 Hc1kc=Hc1kab differ significantly at low temperature (being 5 and 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter H ( c= ab ab= c) that increases from Hc1 at low field to Hc2 at high field.

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

L. Lyard, P. Szabo, Thierry Klein, J. Marcus, C. Marcenat, et al.. Anisotropies of the Lower and Upper Critical Fields in MgB2 Single Crystals. Physical Review Letters, 2004, 92, pp.057001. ⟨10.1103/PhysRevLett.92.057001⟩. ⟨hal-00959095⟩