NMR probe of pseudogap characteristics in Fe2+xV1-xAl

[摘要] We report the results of a V-51 nuclear magnetic resonance (NMR) study of Fe2+xV1-xAl, near the ordered composition with x = 0, at temperatures between 4 and 500 K. All compositions are found to be metallic or semimetallic, though electrical resistivity has indicated a metal-insulator transition at x = 0. The low-temperature NMR relaxation rates for stoichiometric (x = 0) and nonstoichiometric (x = 0.10 and - 0.05) compounds follow a Korringa law, associated with a finite density of carriers at the Fermi level. High-temperature relaxation rates for x less than or equal to 0 go over to a semiconductorlike activated form, providing information about the gap structure near the Fermi energy. The results are consistent with pseudogap features identified by recent band-structure calculations, although with smaller energy splittings. We analyze pseudogap changes vs composition, and compare the band-filling behavior to a recent coherent potential approximation calculation.

[关键词] ELECTRONIC-STRUCTURE;FE2VAL;ALLOYS;CRYSTALLINE;COMPOUND;BEHAVIOR;CO