Kinetics of heat flux avalanches at the first order transition in La(Fe-Mn-Si)$_{13}$-H$_{1.65}$ compounds

TL;DR

This study investigates the heat flux avalanches during the first order phase transition in a magnetocaloric material, developing a thermodynamic model and analyzing how magnetic fields influence avalanche behavior and kinetics.

Contribution

It introduces a non-equilibrium thermodynamic model for heat flux avalanches and experimentally determines the kinetic damping parameter at various magnetic fields.

Findings

Avalanches increase in number as the magnetic field approaches the critical point.

Kinetics of avalanches slow down with increasing magnetic field.

The model accurately fits calorimetry data for Mn=0.18.

Abstract

We study heat flux avalanches occurring at the first order transition in La(Fe-Mn-Si)$_{13}$-H$_{1.65}$ magnetocaloric material. As the transition is associated to the phase boundaries motion that gives rise to the latent heat, we develop a non equilibrium thermodynamic model. By comparing the model with experimental calorimetry data available for Mn=0.18, we find the values of the intrinsic kinetic parameter $R_L$, expressing the damping for the moving boundary interface, at different magnetic fields. We conclude that by increasing field, thus approaching the critical point, the avalanches increase in number and their kinetics is slowed down.