MAGNETIC-PROPERTIES OF 2 COPPER (II)-HALIDE LAYERED PEROVSKITES

The magnetic properties of the powdered layered structures of 3-ammoni umpyridinium tetrabromocuprate(II) and 3-ammoniumpyridinium tetrachlor ocuprate(II) have been studied from 4.2 to 150 K. The data were interp reted using both 1D and 2D series expansions for the Heisenberg model, combined with the appropriate mean-field corrections, yielding interl ayer exchanges with J2h/k values of (-11 +/- 2) K for the chloride sal t and (-52 +/- 7) K for the bromide salt. The intralayer exchange (J1h /k) values were found to be (14 +/- 2) K and (20 +/- 2.5) K for the ch loride and bromide salts, respectively. The new results are compared w ith previous results for the eclipsed layered structure series NH3(CH2 )nNH3CuX4, where X = Br or Cl and n = 2, 3, 4, or 5. As the halide-hal ide separation distance decreases the transition from magnetic isolati on of the layers to a strong interlayer exchange is observed. The new study allows confirmation of the power dependence on the halide-halide separation.