Magnetization Process of the S= 1/2 and 1 Ferrimagnetic Chain and Dimer

We report the results of magnetization measurements on powder samples of [NiCu(pba)(D 2 O) 3 ]·2D 2 O (pba=1,3-propylenebis(oxamato),C 7 H 6 N 2 O 6 ) and [Ni(dpt)(H 2 O)Cu(pba)]·2H 2 O (dpt=bis-(3-aminopropyl)amine, C 6 H 17 N 3 ), which are regarded as the S =1/2 and 1 ferrimagnetic chain and dimer, respectively. The magnetization curve in pulsed magnetic fields up to about 50 T of each compound shows an increase with increasing field at low magnetic fields and reaches a plateau of about 1.1 µ B /(formula unit) which corresponds to about one-third of the saturation magnetization. Magnetization of the former compound in static magnetic fields up to 7 T is compared with that of the latter one in addition to the comparison of results of some numerical calculations. We have found that the ferrimagnetic chain has a ferromagnetic feature at low magnetic fields in contrast to the ferrimagnetic dimer and that the calculated magnetization increases with increasing number of composed spins.