Neutron Scattering Study of ZnCr2Se4 with Screw Spin Structure

Abstract

Neutron scattering experiments have been carried out on a single crystal and powdered specimens of ZnCr 2 Se 4 , a helimagnet, above and below the transition at T N =21.2 K. Below T N , crystal belongs to D 4h 19 . Atomic parameters of Se can be expressed by a single parameter, u =0.3847. Rather small magnetic moment (1.71 µ B at 0 K) and the linear dependence of the length of the screw vector, Q 0 , on the lattice deformation were observed. Anisotropic critical scattering ( J x / J y ≃3) was measured around (4- Q 0 , 0, 0) above T N and Q dependence of the exchange interaction constant, J ( Q ), near Q 0 was discussed. Recent studies by Plumier et al. were critically referred.