Impurity-induced antiferromagnetic phase in a new Haldane-gap compound PbNi2V2O8

Recently, it was reported that a new Haldane compound PbNi 2 V 2 O 8 was discovered and the spin-vacancy-induced antiferromagnetism was found with substitution of Mg 2 + ion (S = 0) for Ni 2+ ions (S = 1) [Uchiyama et al., Phys. Rev. Lett. 83 (1999)632]. In this paper, the effect of substitutions of Cu 2 ions (S = 1/2) and Co 2 + ions (S = 3/2) was studied and it was revealed that this effect varied with the values of the spins of the impurity ions.