  The magnetic structure of the spin-chain antiferromagnet SrCo2V2O8 is
determined by single-crystal neutron diffraction experiment. The system
undergoes magnetic long range order below T_N = 4.96 K. The moment of
2.16{\mu}_B per Co at 1.6 K in the screw chain running along the c axis
alternates in the c-axis. The moments of neighboring screw chains are arranged
antiferromagnetically along one in-plane axis and ferromagnetically along the
other in-plane axis. This magnetic configuration breaks the 4-fold symmetry of
the tetragonal crystal structure and leads to two equally populated magnetic
twins with antiferromagnetic vector in the a or b axis. The very similar
magnetic state to the isostructural BaCo2V2O8 warrants SrCo2V2O8 another
interesting half-integer spin-chain antiferromagnet for investigation on
quantum antiferromagnetism.
