Two-phonon spin-lattice relaxation of rigid atomic clusters

TL;DR

This paper investigates two-phonon spin-lattice relaxation mechanisms in atomic clusters, providing detailed calculations of relaxation rates for different anisotropies and identifying temperature regimes where Raman processes dominate.

Contribution

It offers new theoretical calculations of relaxation rates for uniaxial and biaxial spin clusters, highlighting the dominance of Raman processes at certain temperatures.

Findings

Raman relaxation rates are derived for uniaxial anisotropy.

Transition rates between tunnel-split levels are computed for biaxial Hamiltonians.

Temperature ranges where Raman processes dominate are identified.

Abstract

Spin-phonon relaxation due to two-phonon processes of a spin cluster embedded in an elastic medium has been studied. For the case of uniaxial anisotropy, relaxation rates due to Raman processes and processes involving the emission of two phonons have been obtained. For a biaxial spin Hamiltonian, the rates of transitions between tunnel-split levels have been computed. By comparison with the rates of corresponding direct processes, we have established temperature ranges where the Raman mechanism dominates over the one-phonon decay mechanism.