The quasi-one-dimensional compound CuMn${\left({\mathrm{S}}_2{\mathrm{C}}_2{\mathrm{O}}_2\right)}_2$·7.5${\mathrm{H}}_2$O was synthesized, and its magnetic susceptibility ${\chi }_M$ was measured in the temperature range $T=4.2-240\mathrm{}$ K. The curve ${\chi }_{M}T$ vs $T$ presents a minimum at 130 K and a maximum at $\simeq 7.5$ K where three-dimensional ordering occurs. Magnetization data at 1.3 and 4.2 K in the field range 0-5 T are consistent with an antiferromagnetic interaction between Cu(II) and Mn(II) through the dithioxalato bridge. We present theoretical calculations for isotropic exchange interactions between quantum spins ½ (${\mathrm{Cu}}^{2+}$) and classical spins (${\mathrm{Mn}}^{2+}$). The susceptibility is calculated numerically. This theoretical model fits the experimental data well, allowing the determination of the coupling constant $J$ as -30.3 ${\mathrm{cm}}^{-1\mathrm{}}$. The antiferromagnetic interaction between Cu(II) and Mn(II) metallic ions leads to a one-dimensional ferrimagnetic behavior, characterized for the first time, both experimentally and theoretically.

• Received 23 September 1983

DOI:https://doi.org/10.1103/PhysRevB.29.5144