Field-tunable toroidal moment in a chiral-lattice magnet

Area of Science:

• Condensed Matter Physics
• Materials Science
• Magnetism

Background:

• Ferrotoroidal order, a spontaneous arrangement of toroidal moments, is rare and challenging to tune in existing materials.
• Linear magnetoelectric materials have previously been identified as hosts for toroidal moments.

Purpose of the Study:

• To investigate the magnetic and toroidal properties of the chiral triangular-lattice magnet BaCoSiO4.
• To explore the tunability of toroidal order in novel multiferroic materials.

Main Methods:

• Experimental application of a small magnetic field to BaCoSiO4.
• Observation of metamagnetic transitions using magnetic and toroidal moment measurements.
• First-principle calculations to reveal magnetic exchange couplings and interactions.

Main Results:

• Switching between ferritoroidal and ferrotoroidal phases was achieved with a small magnetic field.
• Multi-stair metamagnetic transitions with equidistant steps in magnetic and toroidal moments were observed.
• An unusual hierarchy of frustrated isotropic exchange and chiral antisymmetric exchange interactions was identified.

Conclusions:

• BaCoSiO4 exhibits a novel ferri-ferroic order driven by frustrated exchange and chirality.
• This material represents a new class of multiferroics with tunable toroidal order.
• Opens new avenues for developing easily controllable toroidal materials.