Magnetic and structural properties of Ce2Fe17-xMnx compounds

The compounds Ce2Fe17-xMnx (x=0-3) were synthesized and their structure and magnetic properties were studied. The compounds crystallize in thr rhombohedral Th2Zn17-type structure. Neutron diffraction study of Ce2Fe17-xMg solid solutions shows that Mn prefers the 6c site and avoids completely the 9d site, whereas the 18f and 18h sites are occupied almost randomly. The compositional dependences of the unit cell parameters at 293 K are non-monotonous. The binary compound Ce2Fe17 shows ferromagnetic behavior; below Theta =94 K and helicoidal antiferromagnetic structure with T-N=206 K. The Neel temperature of the compounds Ce2Fe17-xMnx decreases almost monotonously with increasing Mn content, whereas Theta (x) dependence is non-monotonous. Ferromagnetic order disappears in the range x=0.5-1. Probably, the compounds with 1<x<less than or equal to>2 at low temperatures are inhomogenous ferromagnets consisting of microscopical regions with ferromagnetic ordering. Simultaneously, a short-range helicoidal antiferromagnetic state exists in the latter compounds. A magnetic phase (x-T) diagram is presented. The magnetization curves of the compounds with x=0.5-1 show a metamagnetic transition at similar to (4-7) kOe. (C) 2000 Elsevier Science B.V. All rights reserved.