Tuning the Magnetocrystalline Anisotropy Energy of Magnetic Dopants in Ferroelectric Oxides

Manipulating isolated spins with electric fields is of fundamental interest in physics and also has possible applications in low-power devices. Magnetic dopant atoms inserted into ferroelectric oxide hosts provide an interesting platform to investigate spin control via ferroelectric distortions. Here, manipulating the ferroelectric distortion changes the local crystal field environment of the dopant atom, which influences its spin orientation via the spin-orbit interaction. In this talk, we analyze Fe³⁺ dopant atoms in SrTiO₃ under biaxial strain. SrTiO₃ is an incipient ferroelectric, which is non-polar in bulk but transitions to a ferroelectric state under compressive or tensile biaxial strain. We use density functional theory (DFT) calculations to investigate the magnetocrystalline anisotropy energy (MCAE) surfaces of Fe³⁺ dopants in polar phases of SrTiO₃ under compressive and tensile biaxial strain. We also analyze the MCAE in the non-polar tetragonal bulk phase of SrTiO₃ and explore how octahedral rotations in this phase influence the MCAE. We compare our results to systems with different magnetic dopants and host environments. Our findings shed light on the design principles for optimizing electric-field control of single spin sites in ferroelectric hosts, paving the way for novel magnetoelectric devices.