Spin Precession and Avalanches

TL;DR

This paper investigates how spin precession and avalanches in magnetic materials can lead to a transition from localized instability to an ergodic phase resembling finite-temperature behavior, with implications for understanding magnetic dynamics.

Contribution

It provides a theoretical analysis of dynamical nucleation and phase transition phenomena in spin systems with minimal damping and thermal noise.

Findings

Avalanches can induce a transition to an ergodic, high-temperature phase.

Small damping causes the growth front to spread over a large region.

Theoretical insights into spin dynamics relevant for real magnetic materials.

Abstract

In many magnetic materials, spin dynamics at short times are dominated by precessional motion as damping is relatively small. In the limit of no damping and no thermal noise, we show that for a large enough initial instability, an avalanche can transition to an ergodic phase where the state is equivalent to one at finite temperature, often above that for ferromagnetic ordering. This dynamical nucleation phenomenon is analyzed theoretically. For small finite damping the high temperature growth front becomes spread out over a large region. The implications for real materials are discussed.