Single Crystal Neutron Diffraction Study of High Neutron Absorbing Compound EuGa4

Single crystal neutron diffraction measurement of EuGa4 has been carried out using time-of-flight single crystal neutron diffractometer SENJU at BL18 in MLF/J-PARC. In spite of extremely high neutron absorption of natural Eu (not enriched by Eu isotope), significant numbers of Bragg reflection were observed. Lattice parameters and lattice symmetry above TN (= 15 K) obtained from the positions and systematic extinction of the reflections were well agreed with the predefined results of single crystal X-ray diffraction. Furthermore, magnetic reflections were clearly observed below TN at positions of h+k+l = odd. Thus, antiferromagnetic structure of EuGa4 can be described with a propagation vector q = (0 0 0), which breaks a body-centered symmetry