Irreversible Heat Flow Across Phase Boundaries in Phase-Separated Manganites

TL;DR

This study measures heat flow and entropy changes across phase boundaries in phase-separated manganites, revealing irreversible heat flow and hysteresis linked to competing ground states and energy barriers.

Contribution

It provides direct measurements of heat flow and entropy in phase-separated manganites, highlighting irreversible heat flow and hysteresis associated with phase competition.

Findings

Heat flux exhibits irreversible hysteresis with magnetic field.

Entropy hysteresis increases as temperature decreases.

Heat loss correlates with magnetic viscosity in the phase-separated state.

Abstract

We have investigated the change in entropy with direct measurements of heat flow as a function of magnetic field at fixed temperatures across the entire phase diagram of the phase-separated (PS) compound La$_{0.25}$Pr$_{0.375}$Ca$_{0.375}$MnO$_3$ (LPCMO). At this composition, the compound shows competing charge-ordered/antiferromagnetic (CO/AF) ground states. At a fixed temperature, we observe an increase in hysteresis in the entropy as a function of the applied field. The heat flux shows progressively irreversible hysteresis, which characterizes the energy barriers between the two competing ground states, as the temperature is lowered. The increase in the heat loss correlates with the increase in magnetic viscosity in the phase-separated state. Keywords: manganites, avalanche effect, phase transition, heat flow, DSC, entropy. Corresponding author: allimas@sandia.gov . On 10 April 2020, this JAC-Elsevier article was accepted. Yet, its online publication shows numerous errors: Cut-off text, missing Figure Captions, incomplete Table ... None of which is our fault! This makes our paper hard to read, study and/or understand. This reproduction is our final (error-free!) revision. When citing our refereed paper, please also refer to this arXiv print. Thank you for understanding