Manipulation of spin orientation in iron-doped ferroelectric oxides from first principles

Atomic-scale control of isolated spins by electric fields is highly desirable for future technological applications. Ferroelectric oxides containing dilute concentrations of magnetic dopants provide a possible platform for achieving this functionality. Within a ferroelectric, electric field-based polarization switching changes the local crystallographic environment of a magnetic dopant atom, which via a magnetoelastic interaction impacts its spin directionality. In this work, we explore this concept using the example of Aurivillius-phase oxide Bi₂WO₆ with a tungsten-site Fe³⁺ dopant. By combining group theoretic analysis with density functional theory calculations, we show that ferroelectric switching in Bi₂WO₆ proceeds via a two-step pathway. Magnetocrystalline anisotropy energy calculations reveal that the Fe³⁺ dopant spin substituted into the low-symmetry Bi₂WO₆ crystal structure aligns along an easy axis. By tracking changes to the spin directionality during ferroelectric switching, we show that a 90? switch in the polarization direction leads to a 112? reorientation of the spin-easy axis. We comment on the generalization of our findings to other families of ferroelectric oxides and magnetic dopant species.