Magnetic Hysteresis of Single-Molecule Magnets Adsorbed on Ferromagnetic Substrate.

Single-molecule magnets (SMMs), exhibiting magnetic bistability and a large energy barrier to the magnetization relaxation, are attractive candidates for realizing efficient spintronic devices such as ultra-high-density memories and quantum computers. Here, we demonstrate robust spin-polarization of a quintessential SMM, the double-decker bis(phthalocyaninato)terbium(III) (TbPc2) molecules, adsorbed on the bilayer Co islands on Au(111) using spin-polarized scanning tunneling microscopy, visualizing the switching of the SMM spin with submolecular resolution. Our results reveal that molecular spins of TbPc2 are antiferromagnetically coupled to the magnetization of the Co island, irrespective of the bonding configuration of the molecule. Stable spin-polarization is inferred from the substantial hysteresis observed in the magnetization curves measured over the molecules. This is in contrast to the reports of near-zero remanence for the bulk TbPc2 crystals and the TbPc2 molecules on a nonmagnetic substrate. The observation of a significant hysteretic opening can be attributed to the large magnetic anisotropy barrier of the molecule and the suppression of the quantum tunneling process. We anticipate that our approach of using the substrate to control and enhance the properties of a TbPc2 SMM will accelerate further research toward realization of SMM-based functional spintronic devices.