Magnetic and magnetocaloric properties of La1−xErxFe11.44Si1.56 compounds

Structural, magnetic and magnetocaloric properties of La1−xErxFe11.44Si1.56 (x=0, 0.1 and 0.3) compounds were investigated by X-ray diffraction and magnetic measurements. These compounds have a cubic NaZn13 structure with ferromagnetic structure. X-ray powder diffraction showed that the lattice parameter decreases with increasing Er concentration indicating the introduction of Er atoms in the La–Fe phase. The Curie temperature increases slightly with increasing Er up to x=0.3. Magnetic entropy change ΔSm allowing estimation of the magnetocaloric effect (MCE) was determined based on thermodynamic Maxwell's relation. A large magnetic entropy change was observed for low Er contents, the origin of the large MCE is attributed to the first-order field-induced itinerant-electron metamagnetic transition (IEM). However, a decrease of ΔSm with increasing Er concentration is observed. This reduction in magnetocaloric properties is explained by the fact that the increase of Er content in La1−xErxFe11.44Si1.56 formula drives the Ferro–Para transition towards second order and eliminates the metamagnetic transition.