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 Delta S-m 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 NICE is attributed to the first-order field-induced itinerant-electron metamagnetic transition (IEM). However, a decrease of Delta S-m 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. (C) 2007 Elsevier B.V. All rights reserved.