MOSSBAUER STUDY OF CU0.5FE0.5RH2SEXS4-X

Effects of interatomic separation on superexchange interactions and in teratomic binding in Cu0.5Fe0.5Rh2SexS4-x (0 less than or equal to x l ess than or equal to 2) have been studied by Mossbauer, X-ray and magn etic- susceptibility techniques. The crystal structure is found to be a cubic spinel, and lattice constant a(0) increases linearly with incr easing selenium concentration. Temperature dependence of the magnetic hyperfine field at each site follows the Brillouin function for S = 5/ 2. The longer-range superexchange interaction between second-nearest F e neighbors is weakened much more rapidly by increase of interatomic s eparation than that between first-nearest Fe neighbors. As interatomic distance increases, both Neel and Debye temperatures decrease exponen tially while magnetic hyperfine field decreases linearly. (C) 1997 Els evier Science Ltd.