Li-7 and V-51 NMR study of the heavy-fermion compound LiV2O4
Li-7 and V-51 NMR study of the heavy-fermion compound LiV2O4
复制标题
重费米子化合物 LiV2O4 的 Li-7 和 V-51 NMR 研究
DOI：
10.1103/physrevb.57.8890
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发表时间：
1998
影响因子：
3.7
通讯作者：
D. Johnston
中科院分区：
文献类型：
--
作者：
A. Mahajan;R. Sala;E. Lee;F. Borsa;S. Kondo;D. Johnston
报道了重费米子化合物LiV{sub 2}O{sub 4}中Li和{sup 51}V核磁共振Knight位移、线宽、自旋晶格和自旋弛豫速率数据作为温度T （Li和V核分别为1.5{endash}800 K和74{endash}575 K）的函数。{sup 7}Li Knight位移K在约25k处表现出一个宽的最大值，在4.2 K以下几乎是恒定的，线宽也是如此。{sup 51}V骑士位移在575 K时为负，并且随着温度的降低而强烈减小。在{大约}80k以上，{sup 7}Li和{sup 51}V的Knight位移与磁化率成正比，由斜率可以得到两个原子核的超精细耦合常数。{sup 7}Li自旋-晶格弛豫速率随温度的降低而增加，在50 K左右达到最大值。在5k以下，弛豫速率与正常金属一样随T线性下降，但Korringa积（T{sub 1}T）{sup {minus}1}值非常高。尽管如此，{sup 7}Li - Korringa比值K{sup 2}T{sub 1}T/S{sub Li}在{大约}10k以下，与传统金属一样处于单位数量级，因此表明了重费米液体的行为。通过对{sup 7}Li和{sup 51}V弛豫率数据的分析，我们推断出高温（T{approx_gt}50 K）下V局部矩自旋弛豫率与温度的近似平方根依赖关系。对数据的简化分析得出，局部矩与传导电子之间的交换耦合常数的大小为17 meV，相邻局部矩之间的交换耦合常数的大小为2.3 meV。在低温度下，{sup 7}Li和{sup 51}V弛豫率与均匀重费米液体的预期值的定量差异表明，在我们的系统中可能存在诸如Kondo效应筛选V局部矩和/或动态钒T {sub 2g}轨道占用相关/涨落效应等效应。{版权所有}{ital 1998} {ital美国物理学会}«少
{sup 7}Li and {sup 51}V NMR Knight shift, linewidth, spin-lattice, and spin-spin relaxation rate data are reported as a function of temperature T (1.5{endash}800 K and 74{endash}575 K for Li and V nuclei, respectively) in the heavy fermion compound LiV{sub 2}O{sub 4}. The {sup 7}Li Knight shift K exhibits a broad maximum at about 25 K and is nearly constant below 4.2 K, as is the linewidth. The {sup 51}V Knight shift is negative at 575 K and it decreases strongly as the temperature is lowered. Above {approximately}80 K, both {sup 7}Li and {sup 51}V Knight shifts are proportional to the susceptibility and from the slope the hyperfine coupling constant can be obtained for both nuclei. The {sup 7}Li spin-lattice relaxation rate increases as the temperature is lowered below room temperature reaching a maximum at about 50 K. Below 5 K the relaxation rate decreases linearly with T as for normal metals but with a very high value of the Korringa product (T{sub 1}T){sup {minus}1}. Even so, the {sup 7}Li Korringa ratio K{sup 2}T{sub 1}T/S{sub Li} below {approximately}10 K is on the order of unity as in conventional metals, thus indicating heavy Fermi liquid behavior. From an analysis of themore » {sup 7}Li and {sup 51}V relaxation rate data we infer an approximate square root temperature dependence of the V local moment spin-relaxation rate at high temperatures (T{approx_gt}50 K). A simplified analysis of the data yields a value of 17 meV for the magnitude of the exchange coupling constant between the local moments and the conduction electrons and 2.3 meV for that between neighboring local moments. Quantitative discrepancies in the {sup 7}Li and {sup 51}V relaxation rates at low T from what is expected for a uniform heavy Fermi liquid indicate that effects such as Kondo effect screening of the V local moment and/or dynamical vanadium t{sub 2g} orbital occupation correlation/fluctuation effects may be present in our system. {copyright} {ital 1998} {ital The American Physical Society}« less