科研之友
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摘要
The temperature dependence of the upper critical fields, H-c2, was deduced from magnetization measurements of high- quality Mg1-xAlxB2 single crystals along the two main crystallographic directions. We found that the strong temperature dependence of the anisotropy of H-c2 (gamma(H) = H-c2(ab)/H-c2(c)) in pure MgB2 was drastically affected by Al doping. gamma(H) (T) systematically decreased and as a result, gamma(H) for x = 0.2 became nearly temperature independent. The diminished temperature dependence of gamma(H) with Al doping is attributed to an enhanced anisotropic impurity scattering, which makes the sigma bands less anisotropic.
- 出版日期2008-5
