Metal insulator transition in Fe2VAl1-xSix

Resistivity and ac susceptibility measurements have been carried out in the 4.2 to 300 K temperature range for several samples in the series Fe2VAl1-x Six for 0 < x < 1. All samples crystallise in the DO3 structure, with the l attice parameter showing a systematic linear decrease with Si substitution. The magnitude of the room-temperature resistivity, which is 3.4 m Omega cm for Fe2VAl, decreases drastically even for 1% Si substitution. The tempera ture-dependent resistivity shows a negative temperature co-efficient for Fe 2VAl, which turns positive for samples with c > 0.05. The ac susceptibility measurements show that Fe2VAl is non-magnetic, while they indicate the for mation of a ferrimagnetic phase for x = 0.04, with T-c < 4 K. The results a re discussed in the light of currently known models of the electronic struc ture of these systems. (C) 2001 Elsevier Science B.V. All rights reserved.