Neutron scattering study of ZnCr2Se4 with screw spin structure

Neutron scattering experiments have been carried out on a single crystal and powdered specimens of ZnCr2Se4, a helimagnet, above and below the transition at T sub(N)=21.2 K. Below T sub(N), crystal belongs to D sub(4h)sup(19). Atomic parameters of Se can be expressed by a single parameter, μ=0.3847. Rather small magnetic moment (1.71 μsub(B) at 0 K) and the linear dependence of the length of the screw vector, Q0, on the lattice deformation were observed. Anisotropic critical scattering (J sub(x)/J sub(y) asymptotically equals 3) was measured around (4-Q0,0,0) above T sub(N) and Q dependence of the exchange interaction constant, J(Q), near Q0 was discussed. Recent studies by Plumier et al. were critically referred. (auth.)