Influence of Thermal Cycling on Giant Magnetocaloric Effect of Gd5Si1.3Ge2.7 Thin Film

TL;DR

This study examines how repeated thermal cycling affects the microstructure and magnetocaloric properties of Gd5Si1.3Ge2.7 thin films, revealing significant phase changes and reductions in magnetic entropy change after extensive cycling.

Contribution

It provides new insights into the effects of thermal cycling on the microstructure and magnetocaloric performance of Gd-based thin films used in magnetic refrigeration.

Findings

Hysteresis area decreases by 16% after 450 cycles

Loss of magneto-structural transition after 1000 cycles

O(II) phase significantly reduced due to internal strain buildup

Abstract

In the lifetime of a magnetic refrigerator the materials are subjected to millions of thermal magnetic cycles, so it is of the utmost importance to predict the behavior of such materials when subjected to related work conditions. Thus, in this work we investigated the influence of thermal cycling in the microstructure, magnetic phase transition and magnetic entropy change of a Gd5Si1.3Ge2.7 thin film up to 1000 cycles. In a first stage, till 450 cycles, the hysteresis area of the magnetization curves as a function of temperature was found to decrease 16% with thermal cycling, due to an arresting of the O(II) phase caused by internal strain. Nonetheless, after 1000 cycles there is a clear loss of the magneto-structural transition. For all thermal cycles the O(I) phase remains unchanged. Therefore, prolonged thermal cycling leads to a strong reduction of the O(II) phase, attributed to an internal pressure build-up, caused by the large number of expansion/compression cycles that the O(II) phase undergoes across the magnetostructural transition.