Defect controlled spin state transitions in FePc adsorbed CrI3

Our study employs first principles to explore the impact of spin on iron phthalocyanine (molecule) upon adsorption onto defect-functionalized CrI3. We focus on three stable vacancy defects commonly found in CrI3, created by the removal of ‘-Cr-’, ‘-I-’ and ‘-CrI3-’ units from the pristine CrI3 lattice, analyzing their electronic and magnetic characteristics in both FM and AFM scenarios. Notably, these defects predominantly affect the electronic structure near the Fermi level. The adsorption of FePc, on defect-functionalized CrI3, exhibits reduced stability compared to the pristine substrate. FePc demonstrates two stable spin states, a 2 μB low spin state and a 4 μB high spin state. We present two spin-control mechanisms when FePc adsorbs onto these defect-functionalized substrates. We name these — substrate-induced and molecular spin vector-induced control. The former involves manipulating the magnetic order of the substrate (FM/AFM), leading to molecular spin state transitions. The latter mechanism involves modifying the spin orientation on the molecular Fe atom relative to the substrate's spin (parallel/antiparallel), resulting in molecular spin state transitions. This research proposes novel effective methods to control the spin states of magnetic metal complexes during adsorption onto magnetic substrates, offering potential applications in molecular electronics and spintronics.