Influence of Si substitution on magnetic properties, random anisotropy, and magnetocaloric effect of nanocrystalline Sm2Fe17−xSix

Nanocrystalline iron-rich intermetallic compounds Sm 2 Fe 17− x Si x ( x = 0 , 1 , 1.5 , 2 ) were studied by means of X-ray diffraction coupled with magnetic and magnetocaloric properties measurements. The mechanically alloyed and annealed compounds were single phase and crystallize into the R 3 ¯ m Th 2 Zn 17 -type structure. The favorable ratios of the X-ray atomic factor f Si / f Fe allowed the location of the Si atoms in the R 3 ¯ m structure. The best Rietveld agreement factor assessed for a preferential occupation of Si on the 18 h site. The Curie temperature was found to increase with Si content x from 436 K for x = 0 up to 525 K for x = 2, whereas the unit-cell parameters, measured with a standard element, were found to decrease with Si content. The random magnetic anisotropy model was used to determine the random anisotropy fields and the local random anisotropy constant. These nanocrystalline Sm 2 Fe 17− x Si x systems gave good magnetocaloric properties, which however decreased with Si content from 3.29 J/kg K for x = 0 down to 2.54 J/kg K for x = 2, at low field μ 0 H = 1.57 T.