Vibronic barrier effect of magnetic relaxation in single-molecule magnets

Single-molecule magnets (SMMs) are a group of coordination complexes consisting of magnetic atoms and organic ligands, in which the coupling between the spin and local vibrational modes is of critical importance for magnetic relaxation. Vibronic barriers due to spin-phonon coupling have recently been proven to provide explanations for the under-barrier relaxation and anomalously low Raman exponents, two puzzles that have eluded researchers in this area over the decades and pervaded many experiments. Two studies (Phys. Rev. Lett. 2020, 125, 117203 andPhys. Rev. B2021, 103, 014401) have elucidated them as being a result of a multi optical phonon-assisted Raman process in disguise, which introduces the gist and wide implication of this relaxation mechanism. This theory deductively unifies different magnetic relaxation processes in a quantum way, which can also be applied for more general systems.