Quantum avalanche in the Fe$_{8}$ Molecular-Magnet

TL;DR

This study observes a quantum avalanche phenomenon in Fe$_{8}$ molecular magnets, where spin reversal propagates rapidly without thermal aid, revealing insights into quantum magnetic dynamics.

Contribution

It provides the first spatially resolved measurements of quantum avalanche propagation in Fe$_{8}$ molecular magnets, demonstrating non-thermal spin reversal dynamics.

Findings

Avalanche front velocity ~1 m/sec

Avalanche propagation is unaffected by heat pulse velocity

Spin reversal occurs without thermal assistance

Abstract

We report spatially resolved, time-dependent, magnetization reversal measurements of an Fe$_{8}$ single molecular magnet using a microscopic Hall bar array. We found that under some conditions the molecules reverse their spin direction at a resonance field in the form of an avalanche. The avalanche front velocity is of the order of $1$m/sec and is sensitive to field gradients and sweep rates. We also measured the propagation velocity of a heat pulse and found that it is much slower than the avalanche velocity. We therefore conclude that in Fe$_{8}$, the avalanche front propagates without thermal assistance.