Local Electronic Structure, Magnetic Properties, and Optical Transitions of Nd:YAG: An Integrated Quantum Chemical Methods and Magnetic Resonance Study.

Lanthanide ions embedded in crystalline hosts are central to modern technologies, where their unique magnetic and optical properties arise from spin-orbit coupling shaped by the local coordination environment. Here, we provide a unified computational-experimental framework to probe these interactions for Nd3+ in yttrium aluminum garnet (Nd:YAG). Multiconfigurational variational-perturbative complete active space-based calculations with spin-orbit treatments accurately capture the crystal field splitting, magnetic anisotropy, and intra-4f optical transitions. Complementary low-temperature EPR and ultrahigh-field, fast magic-angle spinning paramagnetic NMR experiments benchmark the calculations and reveal how subtle structural features tune the electronic and magnetic response properties. By linking magnetic observables with optical transitions through the same local environment, our study establishes a general strategy for predicting and rationalizing the multifunctional behavior of lanthanide-doped materials.