Crystal-chirality-dependent control of magnetic domains in a time-reversal-broken antiferromagnet

Chiral-lattice magnets can exhibit a variety of physical phenomena when time-reversal symmetry is broken by their magnetism. For example, nonreciprocal responses of (quasi)particles have been widely observed in chiral-lattice magnets with macroscopic magnetization. Meanwhile, time-reversal symmetry can also be broken in antiferromagnets without magnetization. Here we report an unconventional chirality-magnetism coupling in a chiral-lattice antiferromagnet Pb(TiO)Cu-4(PO4)(4) whose time-reversal symmetry is broken by an ordering of magnetic quadrupoles. Our experiments demonstrate that a sign of magnetic quadrupoles is controllable by a magnetic field only, which is generally impossible in consideration of the symmetry of magnetic quadrupoles. Furthermore, we find that the sign of magnetic quadrupoles stabilized by applying a magnetic field is reversed by a switching of the chirality. Our theoretical calculations and phenomenological approach reveal that this unusual coupling between the chirality and magnetic quadrupoles is mediated by the previously-unrecognized magnetic octupoles that emerge due to the chirality.

Automated summary

Chiral-lattice magnets can exhibit various physical phenomena when time-reversal symmetry is broken by their magnetism, even in antiferromagnets without magnetization. An unconventional coupling between chirality and magnetic quadrupoles was observed in a chiral-lattice antiferromagnet, mediated by previously unrecognized magnetic octupoles emerging from chirality.