The role of anharmonic phonons in under-barrier spin relaxation of single molecule magnets

作者：Alessandro Lunghi, Federico Totti, Roberta Sessoli, Stefano Sanvito · 发表于：Nature Communications · 年份：2017 · DOI：10.1038/ncomms14620 · 被引用次数：465 · 研究领域：Magnetism in coordination complexes、Quantum and electron transport phenomena、Organic and Molecular Conductors Research

The use of single molecule magnets in mainstream electronics requires their magnetic moment to be stable over long times. One can achieve such a goal by designing compounds with spin-reversal barriers exceeding room temperature, namely with large uniaxial anisotropies. Such strategy, however, has been defeated by several recent experiments demonstrating under-barrier relaxation at high temperature, a behaviour today unexplained. Here we propose spin-phonon coupling to be responsible for such anomaly. With a combination of electronic structure theory and master equations we show that, in the presence of phonon dissipation, the relevant energy scale for the spin relaxation is given by the lower-lying phonon modes interacting with the local spins. These open a channel for spin reversal at energies lower than that set by the magnetic anisotropy, producing fast under-barrier spin relaxation. Our findings rationalize a significant body of experimental work and suggest a possible strategy for engineering room temperature single molecule magnets.