Magnetocaloric effect in manganites: metamagnetic transitions for magnetic refrigeration

TL;DR

This study investigates the magnetocaloric effect in specific manganites, demonstrating significant temperature changes during metamagnetic transitions, and introduces a new model to accurately calculate these effects considering non-reversible processes.

Contribution

The paper presents a novel method to calculate adiabatic temperature change in manganites accounting for non-reversible processes during metamagnetic transitions.

Findings

Significant magnetocaloric effect observed during metamagnetic transitions.

Inverse magnetocaloric effect identified in Pr-based manganite.

Model predictions closely match experimental measurements.

Abstract

We present a study of the magnetocaloric effect in La5/8-yPryCa3/8MnO3 (y=0.3) and Pr0.5Ca0.09Sr0.41MnO3 manganites. The low temperature state of both ystems is the result of a competition between the antiferromagnetic and ferromagnetic phases. The samples display magnetocaloric effect evidenced in an adiabatic temperature change during a metamagnetic transition from an antiferromagnetic to a ferromagnetic phase . As additional features, La5/8-yPryCa3/8MnO3 exhibits phase separation characterized by the coexistence of antiferromagnetic and ferromagnetic phases and Pr0.5Ca0.09Sr0.41MnO3 displays inverse magnetocaloric effect in which temperature decreases while applying an external magnetic field. In both cases, a significant part of the magnetocaloric effect appears from non-reversible processes. As the traditional thermodynamic description of the effect usually deals with reversible transitions, we developed an alternative way to calculate the adiabatic temperature change in terms of the change of the relative ferromagnetic fraction induced by magnetic field. To evaluate our model, we performed direct measurement of the sample's adiabatic temperature change by means of a differential thermal analysis. An excellent agreement has been obtained between experimental and calculated data. These results show that metamagnetic transition in manganites play an important role in the study of magnetic refrigeration.