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 underbarrier spin relaxation. Our findings rationalize a significant body of experimental work and suggest a possible strategy for engineering room temperature single molecule magnets.

The role of anharmonic phonons in under-barrier spin relaxation of single molecule magnets / Lunghi, Alessandro; Totti, Federico; Sessoli, Roberta; Sanvito, Stefano. - In: NATURE COMMUNICATIONS. - ISSN 2041-1723. - STAMPA. - 8:(2017), pp. 14620-14626. [10.1038/ncomms14620]

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

LUNGHI, ALESSANDRO;TOTTI, FEDERICO;SESSOLI, ROBERTA;
2017

Abstract

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 underbarrier spin relaxation. Our findings rationalize a significant body of experimental work and suggest a possible strategy for engineering room temperature single molecule magnets.
2017
8
14620
14626
Lunghi, Alessandro; Totti, Federico; Sessoli, Roberta; Sanvito, Stefano
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/1079559
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