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M. Eisterer, H. W. Weber:
"The influence of weak texture on the critical currents in polycrystalline MgB₂";
Superconductor Science and Technology, 23 (2010), S. 034006 - 034010.

The current transport in polycrystalline MgB₂ is strongly influenced by the intrinsic anisotropy
of this superconductor. Untextured bulks and wires are macroscopically isotropic, but the grains
retain their anisotropic properties and the field dependence of the critical currents is much
stronger than in isotropic superconductors. Weakly or partially textured tapes are
macroscopically anisotropic, but the anisotropy of the zero resistivity (or irreversibility) field is
smaller than the intrinsic upper critical field anisotropy, γ. The J_c-anisotropy is field and
temperature dependent and can be much larger than γ. The most suitable parameter for the
quantification of the macroscopic anisotropy is, therefore, the anisotropy of the zero resistivity
field. It is difficult to distinguish between a higher degree of texture at a lower intrinsic
anisotropy and a weaker texture at higher anisotropy and hardly possible on the basis of the
field dependence of the critical current anisotropy alone. The knowledge of the upper critical
field is crucial and angularly resolved measurements of either the critical currents or, better, the
resistive in-field transitions are favorable for this purpose.
(Some figures in this article are in colour only in the electronic version)

http://dx.doi.org/10.1088/0953-2048/23/3/034006

http://publik.tuwien.ac.at/files/PubDat_185519.pdf