DOPING EFFECT OF NONMAGNETIC AND MAGNETIC-IMPURITIES ON MAGNETIC-SUSCEPTIBILITY OF THE HALDANE SYSTEM (CH3)(4)NNI(NO2)(3)

Magnetic susceptibility measurement has been carried out on the Haldan e system (CH3)(4)NNi(NO2)(3) containing non-magnetic Zn2+ and magnetic Cu2+ impurity ions. For each impure system, magnetic susceptibility i s described by the sum of two contributions; one is from the Haldane s tate and the other is a paramagnetic contribution. The latter contribu tion increases proportionally with impurity concentration. For 1D syst em shortened by Zn2+ impurity ions, the paramagnetic contribution obey s the Curie law, and its absolute value of the susceptibility is found to amount nearly 40% of the theoretical estimation for the VBS model where the spin with its value S = 1/2 appears at the both edges of 1D segments. In the case for the system with Cu2+ impurity ions, the para magnetic contribution is much smaller than the results for the Zn2+ im pure systems. This reduction of the magnetic moment of Cu2+ ion for S = 1/2 is qualitatively different from the case for the enhanced moment of Cu2+ ion in the anisotropic S = 1 Heisenberg antiferromagnet NENP.