Intrinsic pinning effect and its enhancement by Al substitution in MgB 2 single crystals

T. Nojima, M. Chotoku, K. Takahashi, H. G. Lee, S. I. Lee

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Anisotropic behavior of pinning properties in MgB2 and Mg 0.88Al0.12B2 single crystals has been studied using torque τ (=M x H) magnetometry as a function of magnetic field H and angle θ between the H direction and the c axis. When the direction of H is apart from the ab plane, we do not observe remarkable pinning effect. On the other hand, as θ approaches 90°, the hysteresis in τ(H) and τ(θ) curve suddenly increases and shows the sharp maximum at θ 90°, which remind us of the so-called intrinsic pinning. However, it is found that this pinning effect is irrelevant to the change of anisotropy γ with temperature in MgB2, and is strongly enhanced in Mg 0.88Al0.12B2 in spite of the decrease of γ with Al substitution. These results may indicate another plane-like pinning mechanism, which is extrinsic and become effective by Al substitution.

Original languageEnglish
Article number052190
JournalJournal of Physics: Conference Series
Issue number5
Publication statusPublished - 2009


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