Magnetic properties of a quantum ferrimagnet:: NiCu(pba)(D2O)3•2D2O

We report the results of magnetic measurements on a powder sample of NiCu(pba)(D2O)(3). 2D(2)O (pba=1,3-propylenebis (oxamato)) which is one of the prototypical examples of an S=1/2 and 1 ferrimagnetic chain. Susceptibility (chi) shows a monotonous increase with decreasing temperature (T) and reaches a maximum at about 7 K. In the plot of chi T versus T, the experimental data exhibit a broad minimum and are fit to the chi T curve calculated for the ferrimagnetic Heisenberg chain composed of S=1/2 and 1. From this fit, we have evaluated the nearest-neighbor exchange constant J/k(B)=121 K; the g-values of Ni2+ and Cu2+: g(Ni)=2.22 and g(Cu)=2.09, respectively. Applied external field dependence of chi T at low temperatures is reproduced fairly well by the calculation for the same ferrimagnetic model.