Competition between itinerant ferromagnetism and spin-density wave antiferromagnetism in FeGa

The metallic magnetFeGadisplays a rich magnetic behavior that includes transitions between a FM ground state to a AFM intermediate state at 68 K and back to a FM state at 360 K. The phase transition at 360 K is accompanied by a discontinuous hysteretic change in the electrical resistivity. In addition, the application of moderate magnetic fields cause a sharp transformation from the AFM to FM state with a critical $H$that grows dramatically with $T$.To explore the cause of this unusual competition of magnetic states, we investigated the magnetic structure of FeGavia extensive single crystal neutron diffraction measurements. These measurements revealed a FM ordering with magnetic moments lying along the crystallographic $c$-axis both below 68 K and above 360 K as well as incommensurate spin density wave order between these temperatures. Our refinement of the diffraction data has uncovered the existence of a small non-coplanar moment which may be the origin of our previously discovered topological Hall Effect.