Multi-step Magnetic Transition in Non-centrosymmetric Compound CeCoGe3

Single crystal neutron diffraction experiments on non-centrosymmetric pressure-induced superconductor CeCoGe3 were carried out in order to reveal a magnetic structure in the ground state. This compound shows multi-step magnetic transitions at T-N1=20 K, T-N2=11.5K and T-N3=7.5 K. We have observed the appearance of the magnetic reflection at (101/2) together with the weaker one at (101/4) and its higher-order harmonics at 2.9 K. These results indicate that the ground state magnetic structure consists of two components with dominant q(1)=(001/2) and q(2)=(003/4). No magnetic peak was observed along (00l), indicating that the directions of corresponding antiferromagnetic moments are parallel to the c-axis. Consequently, CeCoGe3 has at least two Ce sites in the ground state with respect to the magnitude of the magnetic moment.