2024/07/11 by Sayantika Bhowal, Bhowal, Sayantika, Nicola A. Spaldin +1 · 3 citations
Engineering · Materials Science · #FOS: Physical sciences #Magneto-Optical Properties and Applications #Materials Science (cond-mat.mtrl-sci) #Multiferroics and related materials #Solid-state spectroscopy and crystallography
paper · pdf · doi:10.48550/arxiv.2407.08369
openalex publication_date 2024/07/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We investigate the role of electric toroidal dipoles in the prototypical ferroaxial materials NiTiO3 and K2Zr(PO4)2, which undergo ferroaxial structural phase transitions of order-disorder and displacive type, respectively. Using first-principles electronic structure theory, we compute the evolution across the ferroaxial transitions of the local electric toroidal dipole moments, defined both in terms of the vortices formed by local dipoles, as well as as the cross product of orbital and spin angular momenta. Our calculations confirm that the electric toroidal dipole acts as the order parameter for these ferroaxial transitions and highlight the importance of spin-orbit coupling in generating a non-zero atomic-site electric toroidal dipole moment. We find that, while the ferroaxial phases of NiTiO3 and K2Zr(PO4)2 preserve global inversion symmetry, they contain inversion-symmetry-broken sub-units that generate vortices of local electric dipole moments. In addition to causing the net electric toroidal dipole moment, these vortices induce a hidden spin polarization in the band structure.