Low-Temperature Phonoemissive Tunneling Rates in Single Molecule Magnets

TL;DR

This paper calculates phonon-assisted tunneling rates in single molecule magnets, specifically Fe8, using two methods and discusses implications for magnetization in molecular solids.

Contribution

It introduces a novel semiclassical approach and provides accurate rate calculations for phonon-assisted tunneling in Fe8, enhancing understanding of spin-phonon interactions.

Findings

Methods agree quantitatively with previous approaches

Calculated tunneling rates for Fe8 are provided

Implications for magnetization dynamics are discussed

Abstract

Tunneling between the two lowest energy levels of single molecule magnets with Ising type anisotropy, accompanied by the emission or absorption of phonons, is considered. Quantitatively accurate calculations of the rates for such tunneling are performed for a model Hamiltonian especially relevant to the best studied example, \Fe8. Two different methods are used: high-order perturbation theory in the spin-phonon interaction and the non-Ising-symmetric parts of the spin Hamiltonian, and a novel semiclassical approach based on spin-coherent-state-path-integral instantons. The methods are found to be in good quantitative agreement with other, and consistent with previous approaches to the problem. The implications of these results for magnetization of molecular solids of these molecules are discussed briefly.