Magnetic and magnetocaloric properties of a foam composite based on substituted La-manganite in a polyurethane matrix

This work deals with the effect that a porous structure causes on the magnetocaloric properties of substituted lanthanum manganite with the formula La0.67Ca0.28Sr0.05MnO3. A composite with a foam structure was fabri-cated using a polyurethane matrix and embedded manganite particles at three different amounts. The magne-tocaloric effect was determined indirectly by mathematical adjustment of the experimental magnetization curves as a function of temperature, according to the phenomenological model proposed by Hamad. Based on the phenomenological parameters, the magnetic entropy change, Delta S-m (H, T), was calculated at 1.5 T and 3.0 T. Also, the Curie temperature, the relative cooling power, RCP, the heat capacity, Delta C-p, and the order of the ferromagnetic-paramagnetic transition of all the samples were determined. Results show a highlighting increase of the relative cooling power when the manganite particles are dispersed in the polymeric matrix. In addition, the magnetocaloric properties turned out to be a function of the amount of manganite embedded in the matrix. Better results were obtained at a lower manganite content. In all the studied cases, the magnetocaloric properties of the foam composite are better than that of the powder. This behavior is attributable to a change in the interaction state of the manganite particles due to the confinement that they undergo in the polymeric matrix.

Automated summary

This study investigated the impact of porous structure on the magnetocaloric properties of substituted lanthanum manganite. Results showed a significant increase in relative cooling power when manganite particles were dispersed in the polymeric matrix, and the magnetocaloric properties were found to be dependent on the amount of manganite embedded in the matrix. The foam composite exhibited superior magnetocaloric properties compared to the powder, likely due to a change in the interaction state of the manganite particles within the polymeric matrix.