NONMAGNETIC GROUND-STATE IN THE MOLECULAR MATERIAL ND-2[CU(PBA)](3)CENTER-DOT-23H(2)O (PBA=1,3-PROPYLENEBIS(OXAMATO))

The crystal structure of Nd-2[Cu(pba)](3)23 H2O with pba = 1,3-propyle nebis(oxamato) was first described two years ago. It consists of tube- like motifs of the formula Nd-2[CU(pba)](3)(H2O)(9) and noncoordinated water molecules. Each Nd(lll) ion is surrounded by three nearest-neig hbor Cu(ll) ions, and in turn each Cu(ll) ion is situated between two Nd(lll) ions. The magnetic properties of the compound have been invest igated. The magnetic susceptibility presents a rounded maximum around 2.5 K, and the product of the magnetic susceptibility and the temperat ure tends to zero as the temperature approaches absolute zero. This in dicates that the ground state of the compound is quasinonmagnetic, whi ch at a first view is quite an unexpected result. This situation is at tributed to a compensation between the local magnetic moments of the t wo Nd(lll) ions and the three Cu(lll) ions at low temperature. This id ea has been tested with a theoretical model in which the local Kramer' s doublets for Nd (lll) and Cu(ll) interact antiferromagnetically. A c ompensation of the magnetic moments may be expected for a value of the ratio g'(Nd)/g(Cu) close to 1.73 g(Nd) and g(Cu) being the average va lues of the Zeeman factor for the ground Kramer's doublet of Nd(lll) a nd Cu(Il), respectively.