59 Co NMR Study of the Co States in Superconducting and Anhydrous Cobaltates
59 Co NMR Study of the Co States in Superconducting and Anhydrous Cobaltates
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超导和无水钴酸盐中 Co 态的 59 Co NMR 研究
DOI：
10.1103/physrevlett.94.247602
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发表时间：
2005
影响因子：
8.6
通讯作者：
N. Blanchard
中科院分区：
文献类型：
--
作者：
I. Mukhamedshin;H. Alloul;G. Collin;N. Blanchard
在${\ mathm {Na}} {0.35}{\ mathm {CoO}}_{2}$取向粉末及其水合超导（HSC）相${\ mathm {Na}} {0.35}{\ mathm {CoO}}_{2},1.3{\ mathm {H}}_{2}\ mathm {O}$中，$^ b{59}\ mathm {Co}$ NMR谱显示出具有相同$T$独立核磁共振位移张量的单一电子Co态。这些阶段明显不同于${\mathrm{Na}}_{0.7}{\mathrm{CoO}}_{2}$，其中我们解析了三种类型的Co位点。它们的自旋磁化率${\ensuremath{\chi}}^{s}$和轨道磁化率${\ensuremath{\chi}}^{\ mathm {orb}}$的各向异性使我们得出结论，电荷歧化发生在非磁性的${\ mathm {Co}}^{3+}$和两个磁位上，在${T}_{2g}$中约有0.3和0.7个空穴。假设期望的${\ mathm {Co}}^{3.65+}}$电荷，该数据与无水和HSC相中单个Co位点的数据一致。
$^{59}\mathrm{Co}$ NMR spectra in oriented powders of ${\mathrm{Na}}_{0.35}{\mathrm{CoO}}_{2}$ and in its hydrated superconducting (HSC) phase ${\mathrm{Na}}_{0.35}{\mathrm{CoO}}_{2},1.3{\mathrm{H}}_{2}\mathrm{O}$ reveal a single electronic Co state with identical $T$ independent NMR shift tensor. These phases differ markedly from ${\mathrm{Na}}_{0.7}{\mathrm{CoO}}_{2}$, in which we resolve three types of Co sites. The large $T$ variation of their spin susceptibilities ${\ensuremath{\chi}}^{s}$ and the anisotropy of the orbital susceptibility ${\ensuremath{\chi}}^{\mathrm{orb}}$ allow us to conclude that charge disproportionation occurs in a nonmagnetic ${\mathrm{Co}}^{3+}$ and two magnetic sites with about 0.3 and 0.7 holes in the ${t}_{2g}$ multiplet. The data are consistent with those for the single Co site in the anhydrous and HSC phase assuming the expected ${\mathrm{Co}}^{3.65+}$ charge.