Magnetic Field Induced Triple-<i>q</i> Magnetic Order in Trillium Lattice Antiferromagnet EuPtSi Studied by Resonant X-ray Scattering

Abstract

Magnetic order in the magnetic-field-induced so-called A phase of cubic chiral antiferromagnet EuPtSi was investigated by resonant X-ray scattering (RXS) near the Eu L2 absorption edge. The high-intensity RXS signal revealed the triple-q magnetic order of the A phase in a magnetic field applied along the [111] direction. The triple-q order is described by three propagation vectors lying on the plane normal to the magnetic field direction: \(\boldsymbol{{q}}_{1} = ( - \delta _{3},\delta _{1},\delta _{2})\), \(\boldsymbol{{q}}_{2} = ( - \delta _{2},\delta _{3}, - \delta _{1})\), and \(\boldsymbol{{q}}_{3} = (\delta _{1},\delta _{2}, - \delta _{3})\), where δ1 ∼ 0.09, δ2 ∼ 0.20, and δ3 ∼ 0.29. With the high resolution in the reciprocal space achieved in the RXS measurement, it is suggested that the triple-q order strongly couples with the underlying crystal lattice. The triple-q magnetic order is discussed in the context of a magnetic skyrmion lattice where geometrical frustration may play a crucial role.