Theory of deflagration and fronts of tunneling in molecular magnets

TL;DR

This paper develops a theoretical framework for understanding magnetic deflagration and tunneling fronts in molecular magnets, highlighting how temperature and dipolar fields influence front propagation and speed, including conditions for sonic velocities.

Contribution

It introduces a comprehensive theory describing the interplay of thermal and quantum effects in magnetic front propagation, including the role of dipolar fields and external transverse fields.

Findings

Magnetic deflagration propagates similarly to chemical burning in molecular magnets.

Dipolar fields can block or unblock tunneling, affecting front dynamics.

Front speeds can reach sonic velocities under strong transverse fields.

Abstract

Decay of metastable states in molecular magnets (MM) leads to energy release that results in temperature increase that, in turn, positively affects the decay rate. This is the mechanism of recently discovered magnetic deflagration that is similar to regular chemical burning and can propagate in a form of burning fronts in long MM crystals. Near spin-tunneling resonances the decay rate is also affected by the dipolar field (self-consistent with the switching magnetization) that can block or unblock tunneling. There are non-thermal fronts of tunneling in which the magnetization adjusts in such a way that the system is on resonance within the front core, so that the tunneling front can propagate. In general, both dipolar field and temperature control fronts of quantum deflagration. The front speed can reach sonic values if a strong transverse field is applied to boost tunneling.