Predicting Magnetic Properties of Lanthanide-Based Single-Ion Magnets from Ab Initio Electronic Structure Calculations

Lanthanide-based single-ion magnets (SIMs) are promising building blocks for the development of new materials with applications in high-density magnetic memory, spintronics, quantum sensing, and quantum computing. All these applications require SIMs with stable and controllable magnetic properties, which originate from the electron spin of lanthanide ions. Spin relaxation is responsible for the loss of magnetization in high-density memory applications, while spin decoherence is related to the loss of quantum information in qubits used in quantum sensing and computing. We will describe our theoretical and computational efforts to understand the factors affecting the electron spin relaxation and decoherence in lanthanide complexes and to determine the design criteria for multifunctional lanthanide-based SIMs with useful opto-magnetic properties. The focus will be on the complexes with the terpyridine ligands and different lanthanide ions in the gas, solution, and crystal phases. High-level ab initio electronic structure calculations showed that in the gas phase these complexes are characterized by a significant ligand field anisotropy. In the crystal phase, the anisotropy is reduced due to a more symmetric ligand coordination. These small changes in the ligand coordination can lead to significant variations in the electronic structure and affect the magnetic properties of these lanthanide complexes.