Magnetic Properties of a Quantum Ferrimagnet: NiCu(pba)(<b><i>D</i></b>_<b>2</b><b><i>O</i></b>)_<b>3</b>·<b>2<i>D</i></b>_<b>2</b><b><i>O</i></b>

Abstract

We report the results of magnetic measurements on a powder sample of\nNiCu(pba)(D_2O)_3 \\cdot 2D_2O$ (pba=1,3-propylenebis(oxamato)) which is one of\nthe prototypical examples of an $S$=1/2 and 1 ferrimagnetic chain.\nSusceptibility($\\chi$) shows a monotonous increase with decreasing temperature\n(T) and reaches a maximum at about 7 K. In the plot of $\\chi T$ versus $T$, the\nexperimental data exhibit a broad minimum and are fit to the $\\chi T$ curve\ncalculated for the ferrimagnetic Heisenberg chain composed of S=1/2 and 1. From\nthis fit, we have evaluated the nearest-neighbor exchange constant $J/k_B=121\nK$, the g-values of Ni$^{2+}$ and Cu$^{2+}$, $g_{Ni}$=2.22 and $g_{Cu}$=2.09,\nrespectively. Applied external field dependence of $\\chi T$ at low temperatures\nis reproduced fairly well by the calculation for the same ferrimagnetic model.\n