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Li-7 and V-51 NMR study of the heavy-fermion compound LiV2O4

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Title Li-7 and V-51 NMR study of the heavy-fermion compound LiV2O4
 
Creator MAHAJAN, AV
SALA, R
LEE, E
BORSA, F
KONDO, S
JOHNSTON, DC
 
Subject spinel compounds
magnetism
 
Description Li-7 and V-51 NMR Knight shift, linewidth, spin-lattice, and spin-spin relaxation rate data are reported as a function of temperature T (1.5-800 K and 74-575 K for Li and V nuclei, respectively) in the heavy fermion compound LiV2O4. The Li-7 Knight shift K exhibits a broad maximum at about 25 K and is nearly constant below 4.2 K, as is the linewidth. The V-51 Knight shift is negative at 575 K and it decreases strongly as the temperature is lowered. Above similar to 80 K, both Li-7 and V-51 Knight shifts are proportional to the susceptibility and from the slope the hyperfine coupling constant can be obtained for both nuclei. The Li-7 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 (T1T)(-1). Even so, the Li-7 Korringa ratio (KT1T)-T-2/S-Li below similar to 10 K is on the order of unity as in conventional metals, thus indicating heavy Fermi liquid behavior. From an analysis of the Li-7 and V-51 relaxation rate data we infer an approximate square root temperature dependence of the V local moment spin-relaxation rate at high temperatures (T greater than or similar to 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 Li-7 and V-51 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(2g) orbital occupation correlation/ fluctuation effects may be present in our system. [S0163-1829(98)00715-2].
 
Publisher AMERICAN PHYSICAL SOC
 
Date 2011-07-17T15:42:16Z
2011-12-26T12:50:23Z
2011-12-27T05:50:14Z
2011-07-17T15:42:16Z
2011-12-26T12:50:23Z
2011-12-27T05:50:14Z
1998
 
Type Article
 
Identifier PHYSICAL REVIEW B, 57(15), 8890-8899
0163-1829
http://dx.doi.org/10.1103/PhysRevB.57.8890
http://dspace.library.iitb.ac.in/xmlui/handle/10054/4772
http://hdl.handle.net/10054/4772
 
Language en