Interactions in the bond-frustrated helimagnet ZnCrSe investigated by NMR.

The zero field Cr nuclear magnetic resonance was measured at low temperatures to investigate the interactions in the bond-frustrated S = 3/2 Heisenberg helimagnet ZnCrSe. A quadratic decrease of the sublattice magnetization was determined from the temperature dependence of the isotropic hyperfine field. We calculated the magnetization using linear spin wave theory for the incommensurate spiral spin order and compared this outcome with experimental results to estimate the coupling constants. The hyperfine fields at Cr and Se ions provide evidences that the spin polarization of Cr ions is transferred to neighboring Se ions due to the covalent bonding between them, resulting in reduced magnetic moment in the Cr ion. This observation indicates that the Jahn-Teller effect, which leads to distortion inducing spin-lattice coupling, is not completely missing in ZnCrSe.