Manipulation of spin orientation via ferroelectric switching in Fe-doped Bi₂WO₆ from first principles

Electric field control of single spins can probe the fundamental limits of  multiferroic behavior and magnetoelectric coupling. One possible platform to explore this scenario is to form isolated spin centers in ferroelectric materials via inclusion of dilute concentrations of magnetic dopants. We investigate single spin manipulation using the Aurivillius phase ferroelectric oxide Bi₂WO₆ as a host. We propose that the low-symmetry environment provided by the layered crystal structure can enable control of the magnetic dopant spin-axis. Using a combination of density functional theory and group theoretic analysis, we enumerate and explore the intrinsic ferroelectric switching pathways in undoped Bi₂WO₆ and find that a two-step pathway has the lowest energy barrier. Then substituting a Fe³⁺ dopant onto one W site in a Bi₂WO₆ supercell, we explore how the magnetocrystalline anisotropy energy and preferred spin orientation evolve throughout ferroelectric switching. We find that the Fe³⁺ spin aligns along a spin-easy axis and that a 90^o switch of the polarization direction leads to a 90^o reorientation of the spin-easy axis. This work advances our understanding of electric field control of single spins, which has potential implications in the fields of spintronics and quantum computing.