Study of the magnetic and magnetocaloric properties at low-field in Nd2Fe17-xSix intermetallics.

Abstract Magnetic refrigeration could ultimately allow the replacement of commonly-used industrial coolers or household refrigerators, mainly for its potential great efficiency and ecological factors. In the search of good magnetocaloric materials, the iron rich Nd2 Fe 17 intermetallics are regarded as very interesting candidates, due to their significant magnetic properties. To that end, three samples with nominal compositions Nd2 Fe 17 - x Si x ( x = 0 , 0.25 , 0.5 ) were prepared by using an arc furnace, followed by annealing. Structural analysis by Rietveld method on X-ray diffractograms have shown that these alloys crystallize in the rhombohedral Th2 Zn 17 -type structure (Space group R 3 ¯ m ) and that Fe is being substituted by Si in the 18 h Wyckoff position. Magnetic properties measurements revealed that the Curie temperature increases while the magnetization at saturation diminishes with Si content. The magnetic entropy change Δ S M reached a maximum of 3.35 J/kg.K, 2.77 J/kg K and 2.50 J/kg K for an applied field of 1.5 T for x = 0, 0.25 and 0.5 respectively, pointing to a decrease with Si content. The RCP seems however to receive an extensive boost from the Fe to Si substitution. Mossbauer spectra analysis was also performed, in order to confirm the site 18 h as the location of Si atoms in Nd2 Fe 17 - x Si x and the magnetization at saturation.