Magnetocaloric functional properties of $Sm_{0.6}Sr_{0.4}MnO_3$ manganite due to advanced nanostructured morphology

TL;DR

This study explores the enhanced magnetocaloric properties of nanostructured $Sm_{0.6}Sr_{0.4}MnO_3$ manganite, demonstrating broader temperature ranges and superparamagnetic effects, advancing magnetic refrigeration materials.

Contribution

It reports the synthesis and characterization of nanostructured $Sm_{0.6}Sr_{0.4}MnO_3$ with improved magnetocaloric properties over bulk material, revealing size-dependent effects.

Findings

Nanostructures exhibit broader ${ riangle}S_M$ versus T curves than bulk.

Nanotubes show an M-shape profile due to superparamagnetic behavior.

A nanoparticle size threshold limits the transition broadening advantage.

Abstract

The magnetocaloric effect (MCE) is the key concept to produce new, advanced, freon-like free, low cost and environmental friendly magnetic refrigerators. Among several potential materials, $Sm_{0.6}Sr_{0.4}MnO_3$ manganite presents one of the highest MCE value in comparison to all other known manganites; however, its studied was only concentrated on the bulk material. To overcame this lack of the information we successfully produced advanced nanostructures, namely nanoparticles and nanotubes of that highlighted manganite by using a sol-gel modified method. High resolution transmission electron microscopy revealed nanoparticle and nanotube diameters of 29 nm and 200 nm, respectively; and, in addition, this technique also showed that the wall of the nanotube is formed by the nanoparticles with 25 nm of diameter. The magnetocaloric potentials, ${\Delta}S_M$ versus T curves, of the nanostructures were obtained and they are broader than the their bulk counterpart. This increases the useful temperature range of a magnetic refrigerator. But also an undesired M-shape profile for the nanotube sample was observed, due to the rising of a superparamagnetic behavior. These results also evidenced the existence of a nanoparticle size threshold below which the advantage to make the transition wider is no longer valid.