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 rhomboh edral Th2Zn17-type structure. Neutron diffraction study of Ce2Fe17-xMg soli d 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 compo sitional dependences of the unit cell parameters at 293 K are non-monotonou s. The binary compound Ce2Fe17 shows ferromagnetic behavior; below Theta =9 4 K and helicoidal antiferromagnetic structure with T-N=206 K. The Neel tem perature of the compounds Ce2Fe17-xMnx decreases almost monotonously with i ncreasing Mn content, whereas Theta (x) dependence is non-monotonous. Ferro magnetic order disappears in the range x=0.5-1. Probably, the compounds wit h 1<x<less than or equal to>2 at low temperatures are inhomogenous ferromag nets consisting of microscopical regions with ferromagnetic ordering. Simul taneously, a short-range helicoidal antiferromagnetic state exists in the l atter compounds. A magnetic phase (x-T) diagram is presented. The magnetiza tion 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.