Radiation- and Phonon-Bottleneck-Induced Tunneling in the Fe8 Single-Molecule Magnet

TL;DR

This study investigates how intense microwave pulses induce a phonon bottleneck in Fe8 single-molecule magnets, enabling observation of rapid spin tunneling and providing insights into spin-phonon relaxation dynamics.

Contribution

It demonstrates the role of a phonon bottleneck in facilitating fast spin tunneling in Fe8, supported by quantitative numerical simulations of the system's dynamics.

Findings

Radiation induces a phonon bottleneck with a ~5 μs timescale.

Thermally assisted resonant tunneling observed at 100-ns scale.

Spin-phonon relaxation time estimated at ~40 ns.

Abstract

We measure magnetization changes in a single crystal of the single-molecule magnet Fe8 when exposed to intense, short (<20 $\mu$s) pulses of microwave radiation resonant with the m = 10 to 9 transition. We find that radiation induces a phonon bottleneck in the system with a time scale of ~5 $\mu$s. The phonon bottleneck, in turn, drives the spin dynamics, allowing observation of thermally assisted resonant tunneling between spin states at the 100-ns time scale. Detailed numerical simulations quantitatively reproduce the data and yield a spin-phonon relaxation time of T1 ~ 40 ns.