Gapless antiferromagnetic behavior in newly synthesized marcasite-phase CoAsSe*

CoAsSe belongs to the CoXY chalcogenide family and is reported to crystalize in different phases depending on the synthesizing temperature and pressure, including a half metallic phase according to DFT calculations. For the first time, we have synthesized marcasite-phase CoAsSe in large amount to perform neutron scattering measurements. Elastic neutron scattering measurements revealed weak magnetic peaks below T ~ 38 K at momentum transfer positions of (0, 0.5, 0) and (1, 0, 0) in reciprocal lattice units. Detailed inelastic measurements in low temperature revealed a broad excitation spectrum in the energy transfer-momentum transfer map. We will present the magnetic structures of the newly synthesized marcasite phase CoAsSe and discuss its relationship to electrical measurement results.