POET: A Software Suite for Mapping the Site-Specific Electronic Origins of Magnetic Anisotropy.

The growing energy demand of global information technologies motivates the development of sustainable materials capable of retaining and processing information at the atomic scale. Resolving the site- and orbital-specific origins of magnetic anisotropy energy (MAE) is key to establishing the physical principles required for the rational design of tailored atomic-scale magnets. However, these contributions remain obscured in the output of noncollinear density functional theory calculations incorporating spin-orbit coupling. We present the Palacký OptoElectronic Toolkit (POET), an open-access suite that decomposes complex simulation data into intuitive graphical representations that map electronic reorganization onto atomic and orbital contributions and elucidates the interplay between bonding and magnetic anisotropy. To demonstrate its utility, we investigate two complementary strategies for achieving electric-field tunable MAE in transition-metal-functionalized graphene on various substrates. We show that iodination of Pt adatoms on nitrogen-decorated single-vacancy graphene on MgO creates strong, field-tunable in-plane anisotropy, while OsPt and OsPd heterodimers yield exceptional perpendicular MAE of ∼150 meV. The microscopic insights enabled by POET facilitate the rational control of magnetic anisotropy through chemical engineering, paving the way for energy-efficient information storage and processing at the atomic limit.