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

Atomic-scale control of spins by electric fields is highly desirable for future technological applications. Magnetically doped Aurivillius-phase oxides present one route to achieve this, with magnetic ions substituted into the ferroelectric structure at dilute concentrations, resulting in spin-charge coupling. However, there has been minimal exploration of the ferroelectric switching pathways in this materials class, limiting predictions of the influence of an electric field on magnetic spins in the structure. Here, we determine the ferroelectric switching pathways of the end member of the Aurivillius phase family, ${\mathrm{Bi}}_{2}{\mathrm{WO}}_{6}$, using a combination of group theoretic analysis and density functional theory calculations. We find that in the ground state $P{2}_{1}ab$ phase, a two-step switching pathway via $C2$ and $Cm$ intermediate phases provides the lowest energy barrier. Considering iron substitutions on the W site in ${\mathrm{Bi}}_{2}{\mathrm{WO}}_{6}$, we determine the spin easy axis. By tracking the change in spin directionality during ferroelectric switching, we find that a ${90}^{\ensuremath{\circ}}$ switch in the polarization direction leads to a ${112}^{\ensuremath{\circ}}$ reorientation of the spin easy axis. The low-symmetry crystal-field environment of ${\mathrm{Bi}}_{2}\mathrm{W}{\mathrm{O}}_{6}$ and magnetoelastic coupling on the magnetic dopant provide a route to spin control via an applied electric field.