Events

Toroidal moments naturally arise from vortex-like arrangements of spins. Ferrotoroidal order, which represents a spontaneous arrangement of toroidal moments, has recently been found in a few linear magnetoelectric materials. However, tuning toroidal moments in these materials is challenging due to the requirement of a conjugate toroidal field. In this talk, I present the realization of switching between ferritoroidal and ferrotoroidal phases by a small magnetic field, in a chiral triangular-lattice magnet BaCoSiO4 with tri-spin vortices. These vortices are arranged in a staggered fashion in zero magnetic field, giving rise to a ferritoroidal order and non-zero vector and scalar spin chirality, directly coupled with a ferromagnetic component. Upon applying a magnetic field, multi-stair metamagnetic transitions, characterized by equidistant steps in the net magnetic and toroidal moments , develop. Consequently, the system enters in a ferrotoroidal state. I discuss the underpinning physical picture of the this novel ferri- ferroic transition and attribute it to a combined result of an unusual hierarchy of frustrated exchange couplings and the antisymmetric exchange interactions driven by the crystallographic chirality. These findings open up new avenues for realizing easily tunable toroidal orders and spin chirality.