Burstlike first-order transformation studied by semi-adiabatic relaxation calorimetry

V. Hardy,F. Guillou,X. Larose,M. Risser,R. Hamane

doi:10.1063/5.0070977

Abstract

This article reports on a mode of analysis of semi-adiabatic relaxation data allowing to account for exotic phenomena sometimes observed in first-order transitions. The principal interest is to get a detailed characterization of latent heat while using the same experimental configuration as that employed for accurate heat capacity measurements outside the transition. Special attention is paid to the recalescence/antirecalescence effects and to the existence of spikes in the time-dependent exchange of latent heat. The present approach—based on the notion of “power of latent heat”—is shown to be consistent with differential scanning calorimetry, magnetization measurements, and the usual analysis in terms of heat capacity. The study is carried out on a LaFe10.77Si1.23Co0.28 compound that belongs to one of the most promising families of giant magnetocaloric materials.

Highlights

First-order transitions (FOTs) are characterized by the presence of latent heat and a regime in which two phases coexist
The article is organized as follows: in the first part, we present the model allowing to derive instantaneous heat flux exchanges vs time; in the second part, the model is applied to measurements on a LaFeSiCo alloy; the third part is intended to support the reliability of the analysis by comparing the results to Differential Scanning Calorimetry (DSC) data and by showing the consistency with the overall latent heat derived from the Clausius– Clapeyron (CC) equation
Using semi-adiabatic relaxation calorimetry, we have suggested a mode of analysis that is able to account for exotic phenomena scitation.org/journal/jap encountered in FOTs, such as the recalescence/antirecalescence effects and the presence of spikes in the latent heat exchange

Summary

Introduction

First-order transitions (FOTs) are characterized by the presence of latent heat and a regime in which two phases coexist. One among the best known examples is that of recalescence which has been observed for a long time at the solidification of some metallic compounds.[1,2] Basically, this phenomenon corresponds to a transient increase in temperature as the material crosses the transition upon cooling, and its origin relies on a sudden release of latent heat This phenomenon can take place at magnetic transitions, as exemplified by the case of iron reported at the end of the nineteenth century.[3] More recently, related effects have been studied in several magnetic materials for which the symmetrical phenomenon of temperature decreases when crossing the transition upon warming (so-called antirecalescence) was observed.[4,5] The origin of these phenomena, in particular, their connection with the presence of structural defects within the material, was intensively debated. We will adopt the denomination of “reversed trend” in the thermal response to refer to both the recalescence and antirecalescence phenomena

Results

Discussion

Conclusion