Magnetic ordering in (U/sub 0.5/Tb/sub 0.5/)Co/sub 2/Ge/sub 2/, studied by AC-susceptibility and neutron-diffraction measurements

UCo/sub 2/Ge/sub 2/, TbCo/sub 2/Ge/sub 2/ and their intermediate solid solution, (U/sub 0.5/Tb/sub 0.5/)Co/sub 2/Ge/sub 2/, crystallize in the ThCr/sub 2/Si/sub 2/-type structure. AC-susceptibility of the latter at 20-295 K yields paramagnetic values /spl mu//sub eff/=7.3/spl plusmn/0.5 /spl mu//sub B/ and /spl theta/=-50/spl plusmn/15 K. The magnetic structure observed by powder neutron diffraction at /spl ap/10 K is AF-I (+-+-) [with wavevector k=(0,0,1)], characterized by (U,Tb) planes stacked antiferromagnetically with ordered moments along the tetragonal axis. The calculated average ordered magnetic moment per (U,Tb) atom, 4.05/spl plusmn/0.03 /spl mu//sub B/, is compared with those of Tb in TbCo/sub 2/Ge/sub 2/ in UCo/sub 2/Ge/sub 2/, leading to a proposal of ferrimagnetic (U,Tb) planes with antiferromagnetic coupling of U and Tb moments.<
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