Functional LSMO foams for magneto-caloric applications

Abstract

AbstractThe ferromagnetic La$$_{1-x}$$ 1 - x Sr$$_{x}$$ x MnO$$_3$$ 3 (LSMO) manganites are ideal materials for magneto-caloric applications due to their high Curie temperature. Here, we prepare open-cell, porous LSMO foams starting from a commercial polyurethane (PU) foam and commercial LSMO powder with $$x = 0.3.$$ x = 0.3 . The cut PU foams are then covered by a slurry of LSMO powder mixed with PVA and water, and then, the foams are subjected to a heat-treatment with two steps at 600 $$^\circ$$ ∘ C (burn-off organic material) and 1200 $$^\circ$$ ∘ C (sintering/compacting). The resulting ceramic LSMO foams are then characterized by X-ray, SEM, electron backscatter diffraction (EBSD) orientation mapping and magnetic measurements. The foam sample consists of randomly-oriented LSMO grains with an average grain size of 188 nm, being distinctly smaller than bulk samples of the same composition, but considerably larger than LSMO nanowires prepared by electrospinning. The magnetic data reveal a high Curie temperature like the bulk samples, and an entropy change, $$-\Delta S_{\text{M}}$$ - Δ S M slightly higher than that of the bulk samples, which points to a strong influence of the LSMO grain size. Thus, the resulting LSMO foam material is well suited for magneto-caloric applications at room temperature.