Theoretical determination of anisotropic interactions and their modulation by the electric field

Overview & Synopsis

Understanding the origin and control of magnetic anisotropy in transition-metal complexes is a central issue in molecular magnetism, with direct implications for spintronics and quantum information science. This review presents a theoretical framework for the determination of anisotropic magnetic interactions from first principles, with particular emphasis on their microscopic origin and their modulation by external electric fields. We first outline the methodologies that enable the extraction of effective spin Hamiltonians from ab initio calculations, including the treatment of electron correlation and spin-orbit coupling within both first-and second-order regimes. Special attention is devoted to the derivation of physically meaningful isotropic and anisotropic parameters-such as magnetic exchange, zero-field splitting, Dzyaloshinskii-Moriya interactions, and symmetric anisotropic exchange tensors-through effective Hamiltonian theory. The microscopic mechanisms governing these interactions are then analyzed for mono-and polynuclear complexes, highlighting the roles of ligand-field effects, covalence, orbital hybridization, and molecular symmetry. Through selected examples, we illustrate how these factors control both the magnitude and the nature of anisotropic interactions, and how they can be rationalized using quantum chemical wave functions and low-energy electronic spectra. Finally, we discuss the emerging possibility of tuning magnetic interactions via external electric fields. We show how electric fields influence charge distribution, geometry, and exchange pathways, leading to measurable variations in both isotropic and anisotropic magnetic parameters. These results underline the potential of electric-field control as a strategy for achieving magnetoelectric coupling at the molecular scale. Overall, this review highlights how ab initio approaches provide not only quantitative predictions of magnetic properties but also a detailed microscopic understanding, paving the way toward the rational design of molecular systems with controllable and tunable magnetic behavior.