Suppression of zero-field quantum tunneling of magnetization by a fluorido bridge for a “very hard” 3d-4f single-molecule magnet

Single-molecule magnets (SMMs) have been proposed for ultra-high-density information storage due to prolonged relaxation times below blocking temperature (T_B). However, many SMMs suffer from fast magnetization loss at zero-field regime due to the quantum tunneling of magnetization (QTM) effect. Here we show the creation of large ground magnetic momentum is crucial to suppress zero-field QTM for SMMs. The recipe is to use bridging fluoride, which creates ferromagnetic couplings among the lanthanide ions in the complex [Dy₃Cr₃(μ₃-F) (μ₃-OH)₃(mdea)₃(piv)₈DMF]·H₂O·CH₃CN. As such, the molecule owns a large ground magnetic moment of 10.7μ_B and is confirmed to be an SMM with T_B of 5 K. More importantly, a “very hard” magnetic hysteresis loop with a coercive field of 1.3 T and more than 97% remanence is observed up to 0.7 K. Ab initio calculations fully support such observations, rendering the importance of fluorido bridge to suppress zero-field QTM for lanthanide-based SMMs.