Magnetic and structural properties of Ce sub 2 Fe sub 17-x Mn sub x compounds

The compounds Ce sub 2 Fe sub 17-x Mn sub x (x=0-3) were synthesized and their structure and magnetic properties were studied. The compounds crystallize in the rhombohedral Th sub 2 Zn sub 17 -type structure. Neutron diffraction study of Ce sub 2 Fe sub 17-x Mn sub x 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 Ce sub 2 Fe sub 17 shows ferromagnetic behavior below Theta =94 K and helicoidal antiferromagnetic structure with T sub N =206 K. The Neel temperature of the compounds Ce sub 2 Fe sub 17-x Mn sub x 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 < = 2 at low temperatures are inhomogeneous ferromagnets consisting of microscopic 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 approx =(4-7) kOe.