Temperature and Field Dependence of the Anisotropy of <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>MgB</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span>

M. Angst; R. Puzniak; A. Wisniewski; J. Jun; S. M. Kazakov; J. Karpinski; J. Roos; H. Keller

doi:10.1103/PhysRevLett.88.167004

Temperature and Field Dependence of the Anisotropy of ${MgB}_{2}$

M. Angst, R. Puzniak, A. Wisniewski, J. Jun, S. M. Kazakov, J. Karpinski, J. Roos, and H. Keller

Phys. Rev. Lett. 88, 167004 – Published 4 April 2002

Abstract

The anisotropy $γ$ of the superconducting state of high quality single crystals of ${MgB}_{2}$ was determined, using torque magnetometry with two different methods. The anisotropy of the upper critical field was found to be temperature dependent, decreasing from $γ ≃ 6$ at 15 K to 2.8 at 35 K. Reversible torque data near $T_{c}$ reveal a field dependent anisotropy, increasing nearly linearly from $γ ≃ 2$ in zero field to 3.7 in 10 kOe. The unusual temperature dependence is a true bulk property and can be explained by nonlocal effects of anisotropic pairing and/or the $\vec{k}$ dependence of the effective mass tensor.

Received 18 December 2001

DOI:https://doi.org/10.1103/PhysRevLett.88.167004

Authors & Affiliations

M. Angst^1,*, R. Puzniak², A. Wisniewski², J. Jun¹, S. M. Kazakov¹, J. Karpinski¹, J. Roos³, and H. Keller³

¹Solid State Physics Laboratory ETH, 8093 Zürich, Switzerland
²Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw, Poland
³Physik-Institut, Universität Zürich, 8057 Zürich, Switzerland