Analysis of 11B NMR Powder Lineshape of MgB2 in the Normal Conductive Phase
Analysis of 11B NMR Powder Lineshape of MgB2 in the Normal Conductive Phase
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正常导电相MgB2的11B NMR粉末线形分析
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
K. Takegoshi
中科院分区：
文献类型：
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作者：
T. Yamaji;M. Murakami;Jun Fukazawa;T. Shimizu;K. Takegoshi
在6.3 ~ 21.9T的磁场范围内对Mg B 2粉末样品进行了11 B核磁共振（NMR）测量。各向同性的奈特位移，以及四极耦合频率，准确地确定从魔角旋转（MAS）光谱分析其磁场依赖性。然后，这些NMR参数被用来解释其静态粉末图案光谱观察到在不同的磁场，这反映了各向异性的Knight-shift张量和二阶四极耦合张量。我们发现，骑士位移张量和四极耦合都是轴对称的，它们相对于分子框架的取向也被确定。这是首次通过对粉末状MgB 2的B谱线形状的精确分析，实验测定了粉末状MgB 2的Knight-shift各向异性。各向异性很小（约4ppm），这与以前的观察结果一致，表明原子的各向异性很小。
11 B nuclear magnetic resonance (NMR) measurements have been performed on MgB 2 powder sample at several magnetic fields ranging from 6.3 to 21.9 T. The isotropic Knight-shift, as well as quadrupole coupling frequency, was accurately determined from magic-angle spinning (MAS) spectra by analyzing its magnetic-field dependence. These NMR parameters were then used to interpret its static powder-pattern spectra observed at various magnetic fields, which reflect both the anisotropic Knight-shift tensor and the second-order quadrupole coupling tensor. We found that the Knight-shift tensor and the quadrupole coupling are both axially symmetric and their relative orientation to the molecular frame was also determined. This is the first experimental determination of the anisotropy of the Knight-shift of MgB 2 in a powder form from an exact analysis of the powder lineshape of the 11 B NMR spectra. The anisotropy was found to be very small (∼4 ppm), being in consistent with previous observations indicating that ani...