Fabrication of magnetocaloric La(Fe,Si)$_{13}$ thick films

TL;DR

This study successfully fabricates thick La(Fe,Si)$_{13}$ films with properties similar to bulk materials, revealing unique negative thermal hysteresis potentially due to substrate-induced strain energy, advancing magnetocaloric material research.

Contribution

First demonstration of thick La(Fe,Si)$_{13}$ films with comparable properties to bulk, exploring strain effects and negative hysteresis in thin film form.

Findings

Films exhibit bulk-like magnetic and structural properties.

Negative thermal hysteresis observed in the ferromagnetic transition.

Substrate may store strain energy influencing hysteresis behavior.

Abstract

La(Fe,Si)$_{13}$-based compounds are considered to be very promising magnetocaloric materials for magnetic refrigeration applications. Many studies have focused on this material family but only in bulk form. In this paper, we report the fabrication of thick films of La(Fe,Si)$_{13}$, both with and without post-hydriding. These films exhibit magnetic and structural properties comparable to those of bulk materials. We also observe that the ferromagnetic phase transition has a negative thermal hysteresis, a phenomenon not previously found in this material but which may have its origins in the availability of a strain energy reservoir, as in the cases of other materials in which negative thermal hysteresis has been found. Here, it appears that the substrate acts to store strain energy. Our exploratory study demonstrates the viability of thick films of the La(Fe,Si)$_{13}$ phase and motivates further work in the area, while showing that additional perspectives can be gained from reducing the dimensionality of magnetocaloric materials in which the magneto-volume effect is large.