Pump-Probe Experiments on the Single-Molecule Magnet Fe8 : Measurement of Excited Level Lifetimes

TL;DR

This study uses pump-probe microwave techniques to measure spin dynamics and relaxation times in the single-molecule magnet Fe8, revealing microsecond spin-phonon relaxation and nanosecond energy diffusion times.

Contribution

It introduces a time-resolved magnetization measurement method to directly observe spin relaxation and energy diffusion in Fe8 at nanosecond scales.

Findings

Spin-phonon relaxation times are around one microsecond.

Energy diffusion times are approximately 70 nanoseconds.

Temperature dependence aligns with theoretical predictions.

Abstract

We present magnetization measurements on the single molecule magnet Fe8 in the presence of pulsed microwave radiation. A pump-probe technique is used with two microwave pulses with frequencies of 107 GHz and 118 GHz and pulse lengths of several nanoseconds to study the spin dynamics via time-resolved magnetization measurements using a Hall probe magnetometer. We find evidence for short spin-phonon relaxation times of the order of one microsecond. The temperature dependence of the spin-phonon relaxation time in our experiments is in good agreement with previously published theoretical results. We also established the presence of very short energy diffusion times, that act on a timescale of about 70 ns.