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Type: Artigo de periódico
Title: Angular dependence of the bulk nucleation field Hc2 of aligned MgB2 crystallites
Author: de Lima, OF
Cardoso, CA
Ribeiro, RA
Avila, MA
Coelho, AA
Abstract: The angular dependence of the bulk nucleation field of a sample made of aligned MgB2 crystallites was obtained using dc magnetization and ac susceptibility measurements. A good fitting of the data by the three-dimensional anisotropic Ginzburg-Landau theory attests to the bulk nature of the critical field H-c2. We found a mass anisotropy ratio epsilon2 approximate to0.39 that implies an anisotropy of the Fermi velocity, with a ratio of 1.6 between the in-plane and perpendicular directions, if an isotropic gap energy is assumed. For an s-wave anisotropic gap this ratio could increase to 2.5. Besides the fundamental implications of this result, it also implies the use of texturization techniques to optimize the critical current in wires and other polycrystalline forms of MgB2.
Country: EUA
Editor: American Physical Soc
Citation: Physical Review B. American Physical Soc, v. 64, n. 14, 2001.
Rights: aberto
Date Issue: 2001
Appears in Collections:Unicamp - Artigos e Outros Documentos

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