Fronts of spin tunneling in molecular magnets

TL;DR

This paper investigates the dynamics of spin tunneling fronts in molecular magnets, revealing how dipolar fields influence propagating relaxation fronts and identifying laminar and non-laminar regimes with potential for fast front speeds.

Contribution

It introduces a self-consistent model of propagating spin tunneling fronts controlled by dipolar fields in molecular magnets, highlighting different propagation regimes and conditions for initiation.

Findings

Propagating spin tunneling fronts are driven by dipolar fields adjusting to zero bias.

Two regimes of front propagation: laminar and non-laminar with discontinuities.

Front speed can surpass magnetic deflagration speed under strong transverse fields.

Abstract

Dissipative spin-tunneling transitions at biased resonances in molecular magnets such as Mn-12 Ac are controlled by the dipolar field that can bring the system on and off resonance. It is shown that this leads to spin relaxation in form of propagating fronts of tunneling, with the dipolar field adjusting self-consistently to provide a zero bias within the front core. There are two regimes of the front propagation: laminar and non-laminar with discontinuous magnetization and dipolar field. In the laminar regime the speed of the front can exceed that of the magnetic deflagration, if the transverse field is large enough. Fronts of tunneling can be initiated by magnetic field sweep near the end of the crystal.