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arXiv 0802.1236cond-mat.str-elcond-mat.mtrl-sci
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含磁缺陷重费米子LiV2O4的^{7}Li NMR研究

^{7}Li NMR Study of Heavy Fermion LiV2O4 Containing Magnetic Defects

X. Zong, S. Das, F. Borsa, M. D. Vannette, R. Prozorov, J. Schmalian, D. C. Johnston

摘要:

我们提出了一个系统的研究的^{7}Li NMR性能的变化与磁性缺陷浓度高达0.83摩尔%的尖晶石结构的多晶粉末样品和收集的小单晶的LiV 2 O 4在温度范围从0.5到4.2 K。我们还报告静态磁化强度测量和交流磁化率测量在14 MHz的样品在低温下。磁缺陷的存在使核磁共振谱和核自旋-晶格弛豫速率都不均匀。通过假设(i)存在磁点缺陷的随机分布,(ii)在含有磁缺陷的样品中存在与磁纯LiV 2 O 4中相同的重费米液体,以及(iii)磁缺陷和费米液体对磁化和NMR性质的影响是可分离的,可以很好地解释粉末的NMR数据。在单晶中,观察到有些不同的行为。值得注意的是,在粉末样品中的磁缺陷在T ~ 1.0 K以下显示出自旋冻结的证据,而在具有类似磁缺陷浓度的单晶中,在0.5 K以下没有发现自旋冻结。因此,不同类型的磁缺陷和/或它们之间的相互作用似乎出现在粉末与晶体中,这可能是由于粉末和晶体的基本上不同的合成条件。

英文摘要:

We present a systematic study of the variations of the ^{7}Li NMR properties versus magnetic defect concentration up to 0.83 mol% within the spinel structure of polycrystalline powder samples and a collection of small single crystals of LiV2O4 in the temperature range from 0.5 to 4.2 K. We also report static magnetization measurements and ac magnetic susceptibility measurements at 14 MHz on the samples at low temperatures. Both the NMR spectrum and nuclear spin-lattice relaxation rate are inhomogeneous in the presence of the magnetic defects. The NMR data for the powders are well explained by assuming that (i) there is a random distribution of magnetic point defects, (ii) the same heavy Fermi liquid is present in the samples containing the magnetic defects as in magnetically pure LiV2O4, and (iii) the influences of the magnetic defects and of the Fermi liquid on the magnetization and NMR properties are separable. In the single crystals, somewhat different behaviors are observed. Remarkably, the magnetic defects in the powder samples show evidence of spin freezing below T ~ 1.0 K, whereas in the single crystals with similar magnetic defect concentration no spin freezing was found down to 0.5 K. Thus different types of magnetic defects and/or interactions between them appear to arise in the powders versus the crystals, possibly due to the substantially different synthesis conditions of the powders and crystals.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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