Abstract
Samples of Sm2Fe17-xCrx (x = 0.5-3) ball-milled and subsequently annealed at 1425 K, were studied by X-ray diffraction (XRD) using the Rietveld method coupled to Curie temperature T-c measurements and Mossbauer spectroscopy. XRD investigation have shown that for xless than or equal to2, SmFe17-xCrx alloys crystallize in the Th2Zn17 type rhombohedral structure and in the Nd-3(Fe, Ti)(29) type monoclinic structure for x > 2. The Mossbauer studies indicate that the Cr atoms occupy 6c sites in the rhombohedral structure in all cases. For x = 2, the six (6c) Fe atoms are substituted by Cr atoms and the Fe(6c) sites disappear. The Curie temperature increases up to 447 K for x = 1 and decreases to a value of 424 K for x = 2. The increase of T-c was explained by the increase of the distance between the 'dumbbell' Fe(6c) sites from 2.377 to 2.404 Angstrom. The decrease of T-c is assigned to the magnetic dilution of the Sm2Fe17 lattice by substitution of strong magnetically Fe atoms by weak magnetically Cr atoms and the smaller Cr-Fe and Cr-Cr exchange coupling. (C) 2002 Elsevier Science B.V. All rights reserved.