Anisotropies of the lower and upper critical fields in MgB2 single crystals

The temperature dependence of the upper (H(c2)) and lower (H(c1)) 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 Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1...

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Bibliographic Details
Published in:Physical review letters 2004-02, Vol.92 (5), p.057001-057001
Main Authors: Lyard, L, Szabó, P, Klein, T, Marcus, J, Marcenat, C, Kim, K H, Kang, B W, Lee, H S, Lee, S I
Format: Article
Language:English
Subjects:
Condensed Matter
Physics
Superconductivity
Online Access:Get full text
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Summary:The temperature dependence of the upper (H(c2)) and lower (H(c1)) 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 Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately 5 and approximately 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter gamma(H) (=lambda(c)/lambda(ab)=xi(ab)/xi(c)) that increases from Gamma(H(c1)) at low field to Gamma(H(c2)) at high field.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.92.057001