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arXiv · 2412.04362

The spin-phonon relaxation mechanism of single-molecule magnets in the presence of strong exchange coupling

Sourav Mondal·Julia Netz·David Hunger·Simon Suhr·Biprajit Sarkar·Joris van Slageren·Andreas Köhn·Alessandro Lunghi
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Abstract

Magnetic relaxation in coordination compounds is largely dominated by the interaction of the spin with phonons. Large zero-field splitting and exchange coupling values have been empirically found to strongly suppress spin relaxation and have been used as the main guideline for designing new molecular compounds. Although a comprehensive understanding of spin-phonon relaxation has been achieved for mononuclear complexes, only a qualitative picture is available for polynuclear compounds. Here we fill this critical knowledge gap by providing a full first-principle description of spin-phonon relaxation in an air-stable Co(II) dimer with both large single-ion anisotropy and exchange coupling. Simulations reproduce the experimental relaxation data with excellent accuracy and provide a microscopic understanding of Orbach and Raman relaxation pathways and their dependency on exchange coupling, zero-field splitting, and molecular vibrations. Theory and numerical simulations show that increasing cluster nuclearity to just four cobalt units would lead to a complete suppression of Raman relaxation. These results hold a general validity for single-molecule magnets, providing a deeper understanding of their relaxation and revised strategies for their improvement.

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Sourav Mondal, Julia Netz, David Hunger, Simon Suhr, Biprajit Sarkar, Joris van Slageren, Andreas Köhn, Alessandro Lunghi. 2024-12-05. The spin-phonon relaxation mechanism of single-molecule magnets in the presence of strong exchange coupling. https://arxiv.org/abs/2412.04362

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