Comparison of temperature and angular dependence of the upper critical field in Mg1-xAlxB2 single crystals in dirty-limit two-gap theory
Comparison of temperature and angular dependence of the upper critical field in Mg1-xAlxB2 single crystals in dirty-limit two-gap theory
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DOI：
10.1103/physrevb.73.064520
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发表时间：
2006-02-01
影响因子：
3.7
通讯作者：
Lee, SI
中科院分区：
文献类型：
--
作者：
Kim, HJ;Lee, HS;Lee, SI
我们研究了Mg1-xAlxB2单晶（x=0.12和0.21）上临界场[H-c2(T, θ)]的温度和角依赖性，并与脏极限双间隙理论进行了比较。我们发现H-c2（T,）可以用这个理论很好地统一描述。将实验数据与理论拟合得到的参数值表明，随着Al浓度的增加，各向异性杂质散射增加，使sigma波段的各向异性减弱。相应的，温度对H-c2各向异性比（γ (H)）的依赖程度有系统的降低，当x=0.21时，γ (H)几乎与温度无关。我们的结果表明Mg1-xAlxB2单晶处于脏极限，并且双间隙性质持续到x=0.21。
We studied the temperature and the angular dependences of the upper critical field [H-c2(T,theta)] of Mg1-xAlxB2 single crystals (x=0.12 and 0.21) and compared with the dirty-limit two-gap theory. We found that H-c2(T,theta)'s were well described in a unified way by this theory. The values of the parameters obtained by fitting experimental data to the theory indicated that as the Al concentration was increased, anisotropic impurity scattering increased, making the sigma bands less anisotropic. Accordingly, the temperature dependence of the anisotropy ratio of H-c2 (gamma(H)) systematically decreased, and for x=0.21, gamma(H) was nearly independent of temperature. Our results imply that Mg1-xAlxB2 single crystals are in the dirty limit and that the two-gap nature survives until x=0.21.