Microscopic magnetic properties of metallic and insulating V 4 O 7 and V 7 O 13
Microscopic magnetic properties of metallic and insulating V 4 O 7 and V 7 O 13
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金属和绝缘体V 4 O 7 和V 7 O 13 的微观磁性能
DOI：
10.1103/physrevb.9.1230
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发表时间：
1974
影响因子：
3.7
通讯作者：
S. Kachi
中科院分区：
文献类型：
--
作者：
A. Gossard;J. P. Remeika;T. M. Rice;H. Yasuoka;K. Kosuge;S. Kachi
金属和绝缘${\mathrm{V}}_{4}$${\mathrm{O}}_{7}$和${\mathrm{V}}_{7}$${\mathrm{O}}_{13}$中各个原子位点的局域磁性已通过$^{51}\mathrm{V}$核磁共振确定。在金属 ${\mathrm{V}}_{4}$${\mathrm{O}}_{7}$ 和 ${\mathrm{V}}_{7}$${\mathrm{O}}_{13}$ 中发现了明显的类似自由自旋的顺磁行为，尽管在不同位点上没有完全区分为 3+ 和 4+ 电荷态。在 ${\mathrm{V}}_{4}$${\mathrm{O}}_{7}$ 金属-绝缘体转变下方，一组 ${\mathrm{V}}^{4+}$ 离子在绝缘相中形成非磁性单线态自旋对，而其余位点是顺磁性的。在反铁磁绝缘状态下，发现了两个超精细磁场为 70.1 和 78.4 kOe 的磁性钒位点以及一个非磁性钒位点。这些结果根据各种理论模型进行了分析，即修正的哈伯德模型和小极化子模型。没有一个理论模型是令人满意的。
The local magnetic properties of the various atomic sites in metallic and insulating ${\mathrm{V}}_{4}$${\mathrm{O}}_{7}$ and ${\mathrm{V}}_{7}$${\mathrm{O}}_{13}$ have been determined by means of $^{51}\mathrm{V}$ nuclear magnetic resonance. Remarkably free-spin-like paramagnetic behavior is found in metallic ${\mathrm{V}}_{4}$${\mathrm{O}}_{7}$ and ${\mathrm{V}}_{7}$${\mathrm{O}}_{13}$, although there is not full differentiation into 3+ and 4+ charge states on the different sites. Below the ${\mathrm{V}}_{4}$${\mathrm{O}}_{7}$ metal-insulator transition, one group of ${\mathrm{V}}^{4+}$ ions forms nonmagnetic singlet spin pairs in the insulating phase while the remainder of the sites are paramagnetic. In the antiferromagnetic insulating state two magnetic vanadium sites with hyperfine fields 70.1 and 78.4 kOe and one nonmagnetic vanadium site are found. These results are analyzed in terms of various theoretical models, i.e., a modified Hubbard model and small-polaron model. None of the theoretical models is satisfactory.