INCOMMENSURATE SPIN-DENSITY-WAVE IN METALLIC V2-YO3

We show by neutron diffraction that metallic V2-yO3 develops a spin density wave below T(N) almost-equal-to 9 K with incommensurate wave vector q almost-equal-to 1.7c* and an ordered moment of 0.15mu(B). The weak ordering phenomenon is accompanied by strong, nonresonant spin fluctuations with a velocity c = 67(4) meV angstrom. The spin correlations of the metal are very different from those of the insulator and place V2-yO3 in a distinct class of Mott-Hubbard systems where the wave vector for magnetic order in the metal is far from a high symmetry commensurate reciprocal lattice point.